Define "Lose Control".
Do you mean that the unit cannot be given new orders, or that it will do absolutely nothing, or that the player cannot select the unit, etc.
Well, yeah, pausing it should work...
Or you want it to be able to attack or so too ? :S
Just that the player can't select it, and manually give it orders ?
Then try adding the ability "Locust" to it, maybe
Though this will bring some consequences, as when you remove it, there'll be no healthbar on the unit...