Why is this not the solution?

[Jojoya]

IMO I think the loophole here is (SE once again) not realizing that they need to restrict things on a per account per server basis, and not per character.

For example, only one character per account per server should be on any leaderboard, and an account should only have one apartment and one personal house on any given server. SE fixes THAT issue, and we'd likely see a good chunk of apartments released from the system as SE is basically getting forced to do this because there is no way they can ever release enough housing to accommodate the demand in the near future.

There's no need for such per account restrictions when instanced housing, like apartments, is used. Instanced housing is load on entry so it's only consuming server resources when a player enters it. It stops consuming server resources once the player leaves and the instance no longer needs to be loaded.

I can only play one character on my account at a time so the game would only need to be loading one instance for my account at a time. That's totally different from the ward plots that are always loaded regardless of whether a player is present.

All you need to do is look at the other MMORPGs using instanced housing to see how well it works. Do you really think a game like ESO would allow every player character to own every single available housing property in that game (there are over 20 last I checked) if instanced housing was a problem?