As a way to help kds pump in prosperous I think rather than the -Ve land/sci ect gains there us to be when hitting into fort that the kd in prosperous should have -ve military losses when being hit.

Ie. "-40% defensive military losses"

Kds hitting into prosperous would still get max land/sci/plunder gains but at least the defender wouldn't be losing a ton of elites army in when trying to get into shape.