Personally I don't understand the point of surrounding the Jupiter Cannons. If you go the long way to surround them, you can still continue to the objective without having to deal with them. And it isn't like the low level MG still can't wipe out or critically damage a low level team. The cannons also don't provide anything useful from drops (as far as I know).
In contrast if you have high level dolls (+90lvl 5x link) It is fairly simple to just brute force many of them except the 3rd tier night battle ones. The only advantage of this is saving some extra turns so it isn't like it is necessary either, especially since there aren't turn limits and the ones that are are for easy daytime battles.
Fuck the night missions honestly, I admit Itried bruteforcing with one AP RF, max level echelon and I was getting wiped out even by sending 2 echelons to the boss. Then it dawned on me that I can repair the echelons before the boss. Otherwise you need months of free exp and the exact RF or MG to lvl up.
Yeah, I always time the retreat so I can deploy a fresh unit for boss bulli. For bosses GFL seems to reward mobility. Bosses hit far too hard or can allow indirect or penetrative attacks that negate any tanking. You really need mobile units to either adjust the concentration of T-dolls away from the MG, or to move everyone out of the way. Once you figure out a strategy that works it is fun to do. I'm just scared about my resource drain. I'm getting all 9 red card drops per day, but I already spent 20k in resources. Not sure if I am going to last.