They should just expand the Private Room feature and let everyone pay 300,000G for one at the Inn... There is potential for everyone on a server to own a Private Room currently, so it's not like there is some server issue stopping this... Just tie the Free Company Private Room with the Inn one if your Free Company has an Estate to prevent people having two Private Rooms (which I imagine could be a problem).

Then all they need to do is exactly what they've suggested they're doing, and provide services like the Chocobo Stable elsewhere in Eorzea, can do something similar for Gardening too I imagine, or the Workshop... Let a Free Company buy a Workshop in Revenant's Toll for example, and just tie it with the Free Company Estate if they have/obtain one... Then Housing isn't a case of haves and have nots, it's a case of everyone has access to this stuff, but owning a plot in the Housing Ward simply ties it all together in one place.