Would some design be interesting?

I realize that this is an impossibility so late in development of this game, but wouldn't it be nice to design some structures during the campaign? Design castles and perhaps city and fort layouts as you need as you take provinces and such? Your defense somewhat determined by how well you design them? The AI would do this generically, but the player would have some say. Perhaps it would be an exploit determined by the apptitude of an AI of fixed thinking? Perhaps this is too much like the abundance of RTS like games? I just had this thought just now. Perhaps I should have kept it to myself. I have just wanted to design stucture in the game since STW.

Sometimes when I'm playing EB I wish that the TW games would have some sort of city builder aspect to them, like I could zoom in to the city or province and choose where the buildings, etc. went and help manage the province. It would add a lot more depth to the campaign, instead of how it is now where all you can really do is click on little icons to build buildings and adjust taxes.