I loved EQ2's housing system. It was instanced. They had 10 or so models costing different levels of upkeep. Bigger places equaled bigger costs. You could allow your alts full access so that you only needed 1 place for all your toons to live at. You could place many, many types of furniture in it. And the furniture could be placed in ways to look like other things. I remember the big thing was to place stuff to look like a fireplace. I personally turned tables into a stage and had an in-game karaoke stage. That is the kind of system I would want if they implemented housing.
They could add a building off Corusant's Senate Tower area that could be for Apartments. Or Dromund Kass. Or a lot of other planets for an instanced housing area.
I like the idea of being able to customize my ship. But I want a bigger place than my ship. It can feel really tiny.