Personally, I think it would be best if we could only own one house at a time. This would make it more special, and also give you the opportunity to choose a hometown, sort of thing. How to approach this I'm unsure. It seems slightly unbalancing to be able to sell your house, since they're some of the most expensive things in the game. Maybe most of the properties are rented, and when you buy a new house you end your tenure at another. I don't know, would like to hear some thoughts on the matter.
Other small things could also give a more homely feeling. Being able to light and extinguish the fire, drag furniture about, buy works of art for the walls. Opening new dialogue options with your neighbours, getting involved in the local community. A lot could be done to add depth to the houses, and make them homes.
Your thoughts?