This is a summary of the Skype meeting that took place on Saturday, February 21, 2015 based on my notes. The meeting was of middling length, but a disproportionate range of subjects were discussed. The next meeting will probably take place on Saturday, March 7, 2015 at 6:00 PM GMT/UTC. Its topic is to be determined.

For once, I'll include the text log, as I had forgotten to bring something up during the meeting, and so it was discussed via text afterwards with the remaining participants. Good luck following the flow of conversation for the first half of the log; it should be easier to do so alongside the rest of the summary. After "*** Call ended, duration 2:09:09 ***" the conversation becomes easier to follow. (LINK: http://tamriel-rebuilt.org/old_forum/viewtopic.php?p=327282#327282 )

The following subjects are not listed chronologically but, roughly, by importance:

Master Planning: While work on the Thirr River Valley will continue, we are aiming to put a greater focus on planning, especially improving and expanding our Master Plan. We have a rough idea of the context of the Thirr River Valley and what we want to do with it, but before we can work effectively on other regions we will need to have our plans in order, or we will (again) be building a house without first building the foundations.
Having established that, and to that end, as you may have noted if you read the log, we ended up covering a wide array of topics covering all of Morrowind's regions (except for Solstheim) in the rest of the meeting.

Main Quest: While the idea of a separate TR mainquest has been discarded -- or rather the Great House questlines will essentially serve as five TR mainquests of which in any individual playthrough the player must choose one -- expanding on Bethesda's questlines is another matter. We discussed the possibility of extending the Vvardenfell mainquest by linking it to the Tribunal mainquest and reworking the latter, (given our approach to Mournhold, we'd have to recreate that mainquest anyway, and doing so will cause no conflicts), thereby forging a narrative that spans the province and concludes the fates of all of Morrowind's gods save Vivec -- player permitting -- and completing Morrowind's story.

Imperial Guilds: Imperial factions are split into branches along administrative district lines. (The Thieves Guild is probably an exception; the matter wasn't explicitly discussed, but it has no real reason to pay attention to arbitrary Imperial borders). The player will only need to join a guild once; membership is shared between branches. After joining, the player will be able to do quests for any branch.
The player will only be able to become the leader of one district branch, as it would be silly for the player to lead all five/six district branches in the same game. Specifically, the player will become the leader of the branch whose quests he finishes first. This will in no way prevent the player from completing other branch questlines, however; in fact, the player will have to complete other branch questlines to become the overall leader of the Morrowind branch.
As discussed above, it is possible that only local branch questlines will count towards the player becoming archmage of a local branch, while it is possible that only major/final quests of each branch will count towards the player becoming the leader of the Morrowind branch.
The Imperial factions do not necessarily need one overarching questline that links all of the district branches and leads the player directly to the top of the faction, though it is still a possibility. Far more likely is that the individual branches would have individual problems, which would sometimes, but by no means necessarily always, connect to other branches.
Another possibility is for a larger story to be told more subtly; the Mages' Guild trying to spread its influence and monopoly over Morrowind, the Thieves' Guild trying to establish itself and survive in a hostile environment, and the Fighters' Guild often having to weigh its morals with a desire to gain local relevance and respect. While sometimes these themes would be explored via large questlines, in other places they could be referenced via side quests or dialogue or other means.
For the most part, Imperial Guilds ignore House Dres, perhaps having chapters in Tear but otherwise having little to no presence in the Deshaan district. It is possible that Dres quests would be especially challenging, the player having to roam the whole district virtually unaided. The Dres are more unified and prone to react than the Telvanni, and they're so isolationist that the guilds would have little to gain from them anyway.
Another idea that was mentioned but remains to be fully explored is the idea of the Empire, House Hlaalu, the Camonna Tong or some combination of the three using the guilds to further their own goals. The idea is not completely new, especially in the case of the Camonna Tong, considering its ties to the Fighters' Guild.

Fighters' Guild: as above, a common theme of the Fighters guild would be a conflict between ideals and -- basically -- trying to please the locals and earn their trust and, perhaps more importantly, contracts. The guild's involvement with the Camonna Tong may present the largest though not only example, and that storyline will likely span the Vvardenfell, Mournhold and Narsis districts. Another example is the Akamora guild, which tries to curry the favour of the local rival nobles.

Mages' Guild: as in Vvardenfell, individual questgivers will tend to have their own agendas and interests. However, while not necessarily presented directly through a large questline, or even necessarily via an individual branch questline, an overall theme -- again, as above -- of trying to gain influence in Morrowind and strengthening their monopoly on magickal knowledge will be present.
An example of indirect presentation would be the Old Ebonheart questline: while there may be quests that send the player to Indoril lands, which would directly show expansion into the Mournhold district, far more prominent than the Mages' Guild's expansionism will be the Indoril desire to halt the expansion.
This process will likely be well advanced in Velothis; while the Redoran still mostly would not deal with the Mages Guild, the Mages Guild has managed to establish its guildhalls in the district, making for a full guild guide network, and likely has a fairly solid monopoly on magic services, at least outside of the Temple and House Redoran itself. This could connect back to the vanilla Telvanni quest in which the player tries to convince House Redoran to stop the Mages Guild monopoly. Whether that quest would have in-game implications for Velothis guild chapters is another question entirely.
In Telvannis, the Mages Guild will likely remain restricted to Firewatch, likely Bal Oyra, and possibly Helnim as well, depending on what we do with the latter. Either way, they are far from establishing a monopoly in Telvanni lands. (And won't have a monopoly at the end of that questline either; no kill-all-the-councillors-on-the-mainland quests).
Other than that, the guild will likely have five guildhalls in Mournhold district, five in Narsis district, its five (of course) in Vvardenfell district, and the probably only the one hall in Tear for Deshaan district.

Thieves' Guild: unlike the other factions, we don't have to be terribly careful in our placement of Thieves Guild chapters, as long as we make note of their placement. They could potentially have a guildhall wherever it seems like they might get a foothold. One example would be the Dres city of Aldmar on the banks of Andaram, with access to the Thirr River. Unlike the other guilds, the Thieves Guild may have managed to establish itself there to some degree. This does not necessarily mean the Thieves Guild would be more common than the other guilds, though. They are likely to have a rather weak presence in Hlaalu lands, for instance.
For the Thieves Guild in particular the idea that the Empire might hire them as a sort of second covert arm to further their interests was forwarded. The Thieves Guild would probably not be aware of their contractors, and certainly the player would only find out about it late into the questline.
Possibly linked to the above or possibly not, the idea of high-profile Telvannis quests in which the player would be tasked with stealing from Telvanni magisters was mentioned.

Camonna Tong: with the above, there was some discussion on the Camonna Tong; specifically, the idea that it was originally a Dres Tong more or less sent to infiltrate Hlaalu lands which the Hlaalu appropriated for their own purposes. This should not be protrayed as a bitter conflict between the Houses, which are on relatively good terms at the start of the game, but rather a result of the general scheming nature of the two Houses. (Both are secretive merchants, and Dres have their regard for the good Daedra, by all accounts a scheming bunch, on top of that).

House Indoril was also discussed in connection with the above; specifically the various groups that could be used to illustrate the instability of the House: the dissident priests, representing doubt in the Tribunal, the End of Times cult of Tribunal, if we keep it, representing abandonment of Tribunal society and life in the face of the march of time, technically smaller groups like the Syvvit Tong, though they did not come up in the meeting, and the reclusive Indoril of (prominently) Lan Orethan.
A new group was discussed, referred to as 'Daggerlads', though they should get a new name. ('Daggerlad' appears to be a general term, like 'cut-throat' or 'swashbuckler'). They are a recent and apparently spontaneous movement of -- perhaps -- predominantly young Indoril nobles who are violently anti-Imperial. They, and the other factions mentioned above, will have to be discussed further, however.

Imperial forts were shortly discussed. There would be few or none in Hlaalu lands, as Hlaalu wanted to avoid the Imperials becoming too firmly rooted in their lands. Instead, Hlaalu keep their lands mostly safe for Imperial citizens (at least within sight of the Empire) and, where necessary, allow the Imperial Legion small garrisons within their towns. As a result, should the right moment come, the Hlaalu would be able to isolate and crush the small garrisons and erase Legion presence in their lands, thereby also cutting off the main communication network between Cyrodiil and the rest of Morrowind.
There could, however, be some forts in Velothis. This would both show the relative weakness of House Redoran and could also be a good way to incorporate a nice idea from a vanilla book:

The Eastern Provinces Impartially Considered wrote:

In fact, a greater threat to Imperial security lies in the idle legions that the taxpayer spends thousands of drakes to support. The generals of these legions, facing no enemies or opposition within the borders of their provinces, may look with ambition to the West. With their loyal veteran troops and coffers fattened by friendly monopolists, they become unpredictable political factors in the uncertainties surrounding the Imperial succession.

Basically, the legion commander of Velothis could be such an individual, and could be trying to increase his powerbase in Velothis, naturally leading to friction with House Redoran, and possibly his fellow Imperials as well.

In connection with the Mages Guild and Bal Oyra, we shortly discussed Imperial presence in Telvannis and why people have suggested scrapping that settlement. Basically, Imperials shouldn't have much presence in Telvannis, and certainly shouldn't have any settlements in the interior of the district, but Bal Oyra is technically on the edge of Telvanni territory -- like Dagon Fel -- and it makes sense that there would be harbours opening to the ocean for Empire-wide Imperial trade -- like Dagon Fel -- so Bal Oyra isn't necessarily as out of line as it originally seemed.

Daedric quests were very briefly mentioned; namely concerns that the seven Daedra associated with Morrowind will be stretched too thin across our vast landmass, and discussing the possibility of pulling in other Daedra. I personally advocated first figuring out what we have in the way of Daedric content, then figuring out what we want, and whether other Daedra should have associated quests.

The Buffer Zone was shortly discussed, at first in regards to the possibility of it being a location for guild quests. The area seems especially suited for Fighters' Guild quests.
However, the idea was also discussed of placing an Ashlander camp there, the Ashlanders likely having been pushed south as the Hlaalu came into Roth Roryn and began building plantations there. This camp -- among others -- could be used to better explore Ashlander relations with various factions; in this case, in particular, House Hlaalu.
More broadly, we discussed the general topic of Ashlanders in Hlaalu land; that when the land was Redoran they may have been left alone, as the Redoran mostly just protect their lands rather than developing them, that the Hlaalu naturally did not leave the Ashlanders alone and took the choicest bits of land for themselves, and that as a result, aside from malcontent tribesmen and outcasts, a lot of Ashlanders leave their tribes and settle down in settlements, both Redoran and -- perhaps -- Hlaalu, likely including Andothren.

From there, we moved on to the topic of Andothren, specifically its planning document. It held up well, though it needs expanding in a few places. Those changes should follow shortly in the linked thread.

Baan Malur was shortly mentioned in connection with it becoming the capital of Morrowind in the Dragonborn expansion. The city is already grand enough for it, (especially if you remove most/all other Tier Is off the map, as the Red Year did), even putting the passage of two centuries aside, so even disregarding the fact that we're not overly concerned with keeping our lore compatible with Dragonborn, it checks out.

Almalexia was briefly mentioned, but only in shortly going over our proposal for it.