How about rather than buildings decaying, they just become abandoned. Then someone can run up and claim it. It should work the same way buildings convert with joining clans, and can function the same way you can dismantle a decayed building.
It would add diversity to servers, create dungeons since the thralls would still be hostile, add new opportunities for newbies to survive.
It’s definitely worth a try. It would bring me back to playing the game for sure.