Nice ideas, but hardly impossible to make!
You can add new animations of course, but they won't fit to the cannon, when you don't look straight to the gun. You can't look anywhere else, because the animation would look retarded.
You would need to unmount from your horse for the unlimbering animation too, same as above.
To move the cannon is the hardest task, since the current scripts reached nearly its limit and that moving script would influence the whole stability of the game!
Beside the fact, that those animations are nearly unimportant and would need to much time to complete, its nearly impossible to do your suggestions, sorry.
