There's 2 suggestions of things I think would be fun to add to the game...
1) A racial bonus. What I mean is... make it so you can unlock (work for it) a bonus where it might cost less room and board for your own race's people when you use them as slaves or followers. I don't imply it should be for free, but maybe its like 75% cost of room space, or 50% or something. This kind of makes sense because your main character would have more insight into his/her own culture.
2) Another type of feature I hope can be added, is that I hope there's no limit on how many room upgrades you can get. I'm very early on in the game, and I've already maxed out slave housing space. 18/18. :S That means I'm having to turn away a lot of really cool slaves. So I hope the game can be set to let you not have a limit to how many housing upgrades you can buy. Although I'd be totally fine if their cost got really high, to make you work for it. I like working for stuff to make you appreciate it anyway.
Edited in later;
It would also be interesting to have an alchemy item you can make to use as a stamina replenisher when in the dungeon. So you don't have to repeat trips to the dungeon. (Although this could be potentially game breaking if its made too easy...)