I think the placard thing was closer to how housing should have been - the problem is that you never really limited the amount 1 player could own; so they created essentially real estate firms which ran amok and SE over-reacted to it.
Honestly - 1 house per DC
Build a structured market for housing - so if I wish to sell my home; then I must do so through the market system and ANY abuse of that is bannable (essentially if you try to freely trade a 1000 million gil and then also use the market system - the buyer could rat you out to SE and keep your house; thus making it a detriment for you to go outside the system AND encourage folks to rat you out for trying to exploit the market)
--Essentially every home would have a bottom and top market; the longer you own a home the higher your top market value goes. you can sell your home to another player for between what you paid for it from the system; or as high as your current market value permits; this stops rapid house flipping.

Do that and I think you would find everyone that wants one would get a house - then you need only deal with the crying for a Large.