Bro, literally anything can work. Something like Valkyries because they com from the sky and wreck shit can work. Therefore, something like Fury Angels can also work, or TIA - Tactical Intervention Angel.
Fuck nigga, you could even go full generic shit and just call them Bitas, Bipedal Tanks. Or just Juggernauts. Or something like Hercules Trooper, or Goliaths. Fuck anon, just use you're brain, there are a thousand combinations available for you. ATCs. Armored Tactical Colossus. Maybe something as simple as "Mammoths" can work too. Add an "Armor Suit" suffix to a word to make an acronym. I dunno OP, just don't be retarded.