Aloha guys, it's me again

Can anyone of you tell me if it's possible to completely limit battlemap movement?
With some other guys I'm working on a Hunderd Years War mod, and we want to include the earliest form of cannons, but we want to give them the ability to deploy stakes, and we want to make them stationary, like the cannons in the Padua demo. (ofcourse, these were scripted, so that doesn't count really).


So the real question is:
-Can I make it impossible for units to move?
-If I can, will the unit (cannon) still be able to turn?

We want to make sure the cannon can't move, but can turn to fire at something that is not directly in front of him.