1. No, although the AI bringing in new troops anywhere does make the SP game more interesting IMO. The old single entrance was poor.

2. yes

3. some control

I would like to select units to belong to a detachment. This detachment would have a taisho who's rating would determine the likelyhood of his arrival on the field when and where I plan. i.e. 4 selected units enter somewhere on the east side of the map 10 minutes into the game. Asking to enter on the extreme opposite side of the field would add extra time to the ETA. A rookie taisho would have a high chance of being late or getting lost and not appearing at all whereas Tokugawa Ieyasu would almost certainly show up on schedule. Any off map units the enemy may have could also influence the algorithm for arrival. So could the presence of a river or the difficulty of terrain. This would add complexity to the game for sure but the strategic aspect would be fun.