Allow adding of archers, swordsmen to machines.

I got this idea from remembering a scene from LOTR. If we were able to add units on top/ into machines we could do things like moving siege towers that lower a draw bridge onto castles and release units into it. What do you guys think?
I want guys to reload my cannon, so there's a reason to put them inside the armour rather than outside as armour. Perhaps even using ammo magazine blocks.