I sadly know what you mean. I only allow myself 10 units per army and no reserve stacks in range to join battle along with one seige unit (onager, ballista, etc) to make 11. The only problem is that I have to fight out most sieges or I will lose every time in a heavily stacked city since the AI doesn't have the limit I impose on myself. Dealing with the horrid pathfinding is a real pain and I've lost some rather easy sieges this way either because I have a needed unit go galivanting around the walls to test the towers archery skills (not nice when it's my general doing it and he won't stop as I didn't catch him quick enough, so now he retreats along the OUTSIDE OF THE WALL instead of straight out), have units just go dumb and stand around or just holding their fire with a clear LOS to the enemy. Cities are a buggy mess and if the odds unit wise and on the screen are near equal or better in my favor I just hit autoresolve and take my chances. I'd rather not go bald trying to get my units to walk down a bloody street.