[quote]I don't see how that framework would resolve the issue of plot inconsistencies, or players abandoning plot-integral characters. If we went down this route, wouldn't we need a lore-keeping and plot-managing staff member for each domain?[/quote]

Depends how deep you want the lore to be, but I don't see anything wrong with a staff member assigned to each domain. Heck, it makes sense for there to be one specific staff member responsible for each domain.

[quote]Even if such positions were created, what would happen if the absent players return to claim their characters?[/quote]

Simple. Rules and Regulations on absence.

Example: "Absence/abandonment: Players must post at least once per week. If a player stops posting or requests to leave, the GM reserves the right to 
1. Permanently or temporarily pass control of the character to another player,
2. Permanently or temporarily turn their character into an NPC controlled by the GM, or
3. Permanently kill or remove that player's character from the story."

Absences can straight up murder a good RP. Make a contingency plan, and make sure players agree to it.