If mind control is mechanically beneficial to the game then that can be shown prior to playtesting. The case needs to be made and I suspect the result will be that mind control is mechanically beneficial. However card designers need to get in the habit of providing such reasoning for their suggestions.
The only thing i have to say is that permanent mind control is no different to PUing a creature then destroying the original with a lightning.
Temporary mind control weakens that similarity, especially if it is a reasonably low duration for effect.
there are things that we need to consider about it, for example:
If i mind control a creature for 2 turns, and I apply adrenaline to it, when the effect is over, it would make sense that the creature will return to the owner in its new state, still having adrenaline. so what i just did was temporarily benefit myself, but at the same time, caused a negative effect that has the potential to counter myself.
therefore if such a mechanic as i suggested is implemented, then the card is beneficial, because it:
1: has a consequence if you dont use it properly
2: creates a challenge for experienced players to work out a strategy by using such a dangerous effect if they edit the creature in anyway.
3: relates to #2, it may discourage the player to edit the creature in anyway.
those are my reasons.
in conclusion, it creates a new style and difficulty of gameplay.