Imho, a house is probably the worst thing for a player base we can get in a game inspired by Infinity engine series. This is not a TES-like sandbox, so a place to dump stuff and trophies and "rp" is not really required. At least, not in a manner like it is done in TES/F3/FNV.
Keep it simple:
- A car in Fallout 2. Basically just a mount + additional inventory.
- A camp from DA:O.
- A pocket dimension from BG2:ToB.
The latter two could use a lot of improvement, but the ideas are interesting.
Or not:
- A house in Drakensang. Not really fun, barely useful - and completely utilitarian. The one in DA2 is similar.
- Strongholds in BG2. The fact that they are class specific is fun, but imo its too much work for too little output: wouldn't a single but much more developed stronghold with options for different classes/characters be a better idea?
- ...which is basically what we got in NWN2. Which was kind of clumsy and felt like a minigame. This could be fun, but requires a lot effort to make right.
Basically, I'd like to either keep it simple, or a real addition to story/gameplay, but not something in-between, like a gimmick house to keep stuff/decorate and collect companions in. Also, a citadel from Siege of Avalon or a castle from Ultima Underworld 2 are good examples of how to catch the right atmosphere for a player base.