There was some complicated way by adding locust, hiding the unit, adding chaos, unhiding it and removing locust ~didnt really work.
In castlefight its done -afaik- by just catching the order and reordering the LastOrder.
Even easier would to make the creeps being owned by a computer, you can use nuetral hostile and neutral piassive for that, you just have to change some gameplay constants like Guard Distance. Then you can change the owner of the unit, but not its Teamcolor.