Yes now that would be a very good idea.

I personally would like to see much more scripting in battles. For example, an enemy ally arriving in the middle of a battle, or even scripted weather changes.

Scripting an entire campaign would be even better. I really like the idea of more mission-oriented battles. I know the Age of Empires series has something similar to this and I think it would add much more variety and replay value to the game, alongside the existing campaign game.