You know, they could eventually create "expansions" for your apartment, increasing its size. A bit like the aquariums? Since there's like 4-5 grades for those, why not the same for apartments?
Or better yet, treat apartments like the ships in FC houses. You collect mats etc to extend the size of your apartment, maybe up to 3-4 times? Right now the apartments are fine, I abandoned my FC chamber for an apartment and, atm, I don't really feel I need more room. Not yet.. anyway...

In my new apartment like;