I like this idea and want to see it implemented all over, either via reclaiming as you mentioned or destruction as per usual. However I dunno how it would look like or if it would cause problems to have hourglasses everywhere… maybe just make it permanent but then I wonder about that too. I suppose it wouldn’t matter to reclaim and just leave it at that unless whoever conquered has some important backstory which they could easily establish to justify hourglasses everywhere.
Make time a fundamental thing moving forward and that solves half the dilemma.