It's a tricky question I've encountered when playing against a Brotherhood army and another topic recall me today (but such problem may be encountered with Capitol and Bauhaus). My adversary uses its first order assignation on a unit A, activates it, spends its actions normally, then plays the Will of the Cardinal command card in order to remove the assigned order token, and finally assigns the second order to the same unit A (as this unit is considered unactivated).
The same principle may be reproduced with Mith Hunter's unit action or the Venusian Ranger Sergeant if you play a command card during its last action.
After reading pg. 12 from the rulebook, its appears that process is illegal. It is mentionned twice that the player must assign the second order to another unit during the turn.
That means, with this kind of game effect, a same unit may play several times during a game round but not during the same turn.