A possible solution to the housing system that wouldn't be too hard to do, maybe...

[Eldevern]

...

The main difference between an apartment and a little house is client side if we consider instancied system. It is a problem ONLY because of wards. Many people would be glad enough with full instancied house.
If they care that much about data, just let people chose : an apartment or a house but not both.

Currently for one player we can have : one house (even an estate), one apartment (several if alts) and one FC room (several if alts) (I don't consider the inn or the FC house). Ok it my point of view but I'm ready to drop apartment and FC room for an instancied estate on floating island or airship.

[AnnaRosa]

The main difference between an apartment and a little house is client side if we consider instancied system. It is a problem ONLY because of wards. Many people would be glad enough with full instancied house.
If they care that much about data, just let people chose : an apartment or a house but not both.

Currently for one player we can have : one house (even an estate), one apartment (several if alts) and one FC room (several if alts) (I don't consider the inn or the FC house). Ok it my point of view but I'm ready to drop apartment and FC room for an instancied estate on floating island or airship.

Yes maybe the instanced home as you describe could be one of the possible solutions, because currently SE provides 4320 plots per server without mention the aps if Ishgard house area actually happen and in the same system there will be 5400 plots even with aps might not be enough for the most crowded servers.

Based on a non-official census page were they base their research results on Lodestone they estimate just Ragnarok to have 11 478 active characters and it's not the most populated server it loses to Zodiark for a few margin, from those 11 478 only 7867 are until the present day 70 lvl because after transfers happened and the server was reopened there were a flood of recently players.

5400 plots (if ishgard happen in the same system) plus aps won't be enough to accommodate 11 478 active characters.