(Map above is multiple screenshots put together..)
With psi attacks we can map up the entire base without leaving the loft we started in.. We used first turn to drop smoke grenades down on level below. I didn't seem to be able to throw from top to bottom floor before I had explored the below, but after first one took the elevator down, somebody on top could throw a grenade down.. One person went down and up again and looked around. Saw nothing.. Then a couple of turns where we went down, saw nothing, and tried to throw a flare in a direction we couldn't see very far, and then move back up on the loft. After a few turns we spotted the first muton and mind controlled him, and only a few turns after we had mapped the entire base, with just a couple of muton casualties..
After the turn from the image above, the turn timer seemed instant, as if we had mind controlled everyone, so think this is about it. Max one more alien I think, but I'm guessing none. All the mutons have dropped their weapons, so only the terror troops should present a risk unless we've missed an alien.
Trouble now is to keep track of where we left all the mind controlled aliens so we can reacquire them next turn. Positioning them in a chain so one of them see the next, works very well as we by mind controlling one will spot the next one. Not so easy everywhere while exploring fast though, so have to remember a few aliens that need to move to spot the next one, and in the image above, the muton all to the east (or north east if you tilt your head right) have explored too fast and likely won't be reacquired next turn. Only two entrance to cover though, and he's unarmed and it looked to be noone else there, so we expect to seem him come to us soon. The turn after we confirmed that the base isn't anything more than what we see above. There's a second floor on some modules, and we've cleared them and we're moving out some of our troops to make it easier to spot all aliens next turn...
Now the question is where to gather them for some reaction and fire practice.. The control center looks interesting as it's only one exit to cover. There's enough mutons for everyone to empty a pistol clip, so I think we'll just starting to execute the terror units which suddenly can become dangerous if we forget to mind control them a turn..