I think this sounds like a very fun mechanic - well, more than a mechanic, I suppose, and more of a system. In many applications a 'Stronghold' was usually nothing more than a mechanic, a method to let the player obtain a house or other dwelling during the course of the game. And often couldn't use it for much even when they did have it.
So kudos to taking it further without trying to over do it!
(And Kudos for your SSI 'cover art'! I so have that game, got it with a bundle of others and still love them!)