This is probably already suggested but... how about the Menacer as a camo for Assault Rifle or Launcher? Maybe a multi-type camo where it turns twin machineguns into the front half of the Menacer. Given the design of the Menacer I believe it will fit well with PSO2's sci-fi aesthetic. As far as I'm aware such a camo is not in the game and would like one.
I did thought of how such guns as the Light Phaser and the Virtua Gun could be made into camo but... I don't really imagine these guns as the twin machineguns sort, and usually the Master System or Sega Saturn came with one of these light guns than two. Maybe they could be gunblade camo's givewn the gunblade is the only single-hand gun in the game but without something to serve as a blade I can't see it happening.