I'm pretty sure it won't work.
IIRC Dominions uses tables of prerandomized numbers, and to show a battle again just means starting at the right place in the right table and recalculating the whole thing all over again.
If you simulate more than one battle at once, you can't tell which random numbers belong to which battle, since they'll all be taking random numbers randomly.
I'm not really explaining this well, but I hope you understand anyway
EDIT: Just to be clear, I'm not saying "impossible!"*, I'm just saying "harder than you think."
*-obviously it is impossible, even if at the worst case scenario it would take rewriting the entire source code from scratch