That would indeed be the awesomest idea. Preparing for the upcoming attack, and permanently strengthening your defenses, would definitely improve playability of Strat.
It would also be awesome if the defenders would have the ability as in Single player campaign, to build improvements in their fiefs, with long time and resources needed to build one, but in the end worth the effort and cost, i.e. water moth, additional archer towers, stone wall for villages etc.