Forcing players to pay to keep housing is unfair.

[Niwashi]

I feel like basing housing demolition off of active subscription isn't exactly the best idea because it's open for potential "abuse."

Housing demolition exists so that players who have left the game don't keep holding those plots in perpetuity, leaving the housing wards as ghost towns of former players. But players who have left the game aren't going to keep their subscription active. (Well, maybe briefly if they forget to turn off auto-renewal, but not for long at any rate.) The ones who are still paying their sub are still continuing the game, and should have the same rights as any other active player.

The "abuses" you describe are nothing of the kind. Sure people could keep their house without making good use of it, but they can already. You don't have to do anything more with it than step inside. (You can also already lose an estate while making regular daily use of it if your use is outside in the garden and you're not keeping careful enough track of that demolition timer.) Demolition isn't about giving plots to people who will use them better.

If the 45 day demolition timer only counted how long you went without an active subscription, and the NPC who holds your goods for you after demolition did so permanently, for the sake of players who take breaks longer than that, it would be a much more balanced and fair system. But SE would still need to deal with their housing shortage issue. Even if their design doesn't allow for keeping houses for all past players (as instancing them could), they do need a system that can readily accommodate all currently active players.