Most excellent writeup, worthy of stickying !

I'd like to add just the one thing : forget cavalry charges in cities, sieges and the like. Just forget it. You will NEVER pull a cavalry charge off in a narrow street, because your knights will keep on "clipping" with the buildings around them (i.e. the street's invisible forcewalls). The only place you can charge somewhat correctly inside a city is in that wide gap between the wall and the town's first buildings. That's it.

(And, despite this being the result of a buggish game mechanic, i'd say it's quite historical to expect horsemen to die inside a city, just like modern tanks get blown up/disabled oh so easily when streetfighting. Cavalry, armored or not, on horse or treads, needs open fields to work. Streets and cities are infantry grounds.)