I thought mission 7 was pretty easy, as I made it to A grade on the first try.
There's not a lot of way to finish it, and I'm in the process of detailing a perfect strategy for it, turn by turn.
The trick is to not be scared by Selvaria. Most people are scared, so they waste time getting themselves destroyed by her. I put my heavy firepower spread near the temple, and never touched them while Selvaria was there watching.
If you move while she's watching, you're dead. But if you don't move, she just ignores all of your men to go save his master.
I had only an Engineer and a Lancer to do most of the job of destroying the turrets and the radiators.
These are the two units Edelweiss had to protect.
The second Lancer joined for the last batch of destruction.