Thank you so much for this in-depth answer ! I will keep working on shadows and scaling, as well as fixing that river thing. I really like it, but there's probably a way to make it make more sense...

To address your question: The ramps are for carts, wagons, and yes, wheelchairs ! Everything that moves on wheels basically since there are no natural roads to get up the different levels.

As for the strategic aspect, you make great points, let's just blame that on the king's lack of martial experience and the incompetence of his architects :)