Armored Core VI Walkthrough - NG Ch1 M10 "Investigate BAWS Arsenal No.2" S-Rank

Take a head that can scan decently and with quick refresh. Something with some kind of aerial endurance would be useful too, as the end fight requires a bit of vertical climbing for three of the enemies and you DON'T want to be out of energy when you hit the ground.
You'll note I've switched to three arm weapons. Handguns are great for this mission, as these guys stay put long enough to stagger them, then you can melee punish. Put the handguns on the shoulders so your right hand is empty going in. Punching is great for stagger, and you can close the gap pretty quick with it too.
Anyway, aside from the fact that these guys are literally invisible until they open fire, there's not much challenge until the last section if you get them on a scan while closing range.
For the last section, get the wall hanging guys one at a time, ignoring the guy with the big electric whip. You can either scan or follow their shots back, they don't move until you get close or hit them. Once you've got the three guys imitating geckos, you can move on to the one with the whip.