Spawning in all is way off..
1. in battle when you killed most enemy's the AI reinforcement spawns here and there and sometimes just a single unit sometimes a little more. they should spawn outside the zone and march in, and then join the battle, that would be real cool. maybe from 3 different sites.
2. Spawning in sieges is a pain, when you finally get inside the walls and killed most enemy's the reinforcement spawns in the centre of the castle or right in front of the gate and right between or behind you and you men. they should spawn inside the castle 'tower' or main house if you like (the building they flee too), and then run out to join the fight.
3. This is not the same i know, but when creating a new character. you don't spawn in the chosen culture area, but always the same spot, this should be fixed too, you could spawn on a coastline with a boat or in a town or something else. it should just be in the area of your chosen culture.