There are two TR factions that do not yet exists as in-game factions in the Tamriel_Data. These are the Imperial Navy and the Imperial Archaeological Society, both of which have their Morrowind headquarters in Old Ebonheart. It would be very useful to have them as proper Factions. After scouring through the old forums I found some threads that discussed the Archaeological Society faction; its ranks, favored skills and requirements. Navy had no such thread, but it should for the most part follow the Legion in terms of favored skills and requirements.
I've taken the liberty of making a proposal of what the two factions could be.
T_Mw_ImperialNavy "Imperial Navy"
Favored Attributes: Endurance, Personality (same as Legion's)
Favored Skills: Athletics, Spear, Long Blade, Blunt Weapon, Block, Light Armor (Legion favors Heavy Armor--otherwise these skills are the same as theirs)
Ranks: 0 Deckhand, 1 Oarsman, 2 Mariner, 3 Boatswain, 4 Captain, 5 Knight Argonaut, 6 Knight Commodore, 7 Knight Navarch, 8 Knight of the Drake Helm, 9 Admiral of the East Fleet
T_Mw_ArchaeologicalSociety "Imperial Archaeological Society"
Favored Attributes: Intelligence, Personality
Favored Skills: Armorer, Acrobatics, Mercantile, Unarmored, Speechcraft, Security
Ranks: 0 Digger, 1 Assistant, 2 Excavator, 3 Senior Excavator, 4 Historian, 5 Curator, 6 Dean of the Society
I've attached an esp file with these two factions. I had forgot how tedious it was to add the Reactions from and towards other factions, so those are only partly finished. Generally other Imperial factions (sans the Thieves Guild) would probably react favorably to the Navy and the Archaeological Society.