Very interesting and elaborated ideas there Psion (hope this will turn to be the main housing thread without having fragmented topics/posts around ^^).
I would add some sort of "reward" when you rest in the house, so the players are encouraged to visit it often. Because we know, some players want their reward to do everything eheh (not me though).

This reward could be a bonus for the fatigue. For example, if you have a rest of several hours, your fatigue could decrease faster than the normal and when fatigue reaches 0, you could gain some "rest bonus" points for every hour. This increases the exp/sp you'll gain for a certain amount of time after the rest. This sort of bonus could increase if your house becomes more comfortable (adding particular furnishings), so the players are encouraged to make fornitures too.
Another idea could be this: more you work on the house (adding fornitures or expanding it), more you become 'expert'. I'd add a new rank bar for this porpouse. Every new rank you'll have a new "title" -visible for other players in the housing section in your /check page- (ex. amateur, interior designer, master architect and so on). And every rank will give you a bonus as well. This bonus could affect the next forniture you'll put in the house or all the fornitures you already have (if every item will have a bonus like in FF11, this bonus could increase depending of your rank).
Another 'reward' for this could be that if you reach a certain rank, you'll be able to make "projects" on sheet to sell (map of the house you create/furnish, complete with fornitures position and stuff). This map could be generated by game poligonally or drawn by you with an in-game paint-system (but maybe this could be too time-consuming to create by the devs).
Concluding, housing should have a little but integrant part in the game (interacting with other in-game systems and other players) and not an activity with visual porpouse only imo. I'll add other ideas when i'll have them more elaborated (and suitable) in mind.
