Some faction quests demote the player, not usually interesting (failure state=reload) but it's useless if advancement isn't at least temporarily blocked at the questgiver's location. Demoting doesn't lower the faction reputation that lets the player get promoted again.

See uses of PCLowerRank

already does it correctly:
TR_m2_FG_Irano2
TR_m3_IL_Purloined

probably not:
TR_m1_FG_Jana      (typo burgalled=burglared)
TR_m1_HT_Dr2

Remember not to demote if rank is 0 or 9 (demoting 0 is useless and MCP option removes faction membership, 9 outranks questgivers and can't get promoted again).
When blocking advancement at the questgiver's location the player can just get promoted by another NPC. If you block advancement globally, your only option to unlock it is time, with a global script, or checking specific quest states for the questgiver's next quests or if you give a task to make amends. The only general parameter for completing quests from other questgivers is faction reputation and you can't check that value because the script function crashes, you can only check if the player has enough reputation and skills for the next rank using the dialogue condition "Rank Requirement".