The mech I took through the game ended up using an unarmed style, complete with Kaio-Ken and a Hermit Purple-like Epyon whip as a secondary weapon to deal with larger groups. Unarmed style opens up a shoulder bash attack that's powerful enough to blow off all of an enemies limbs at once, which then can lead to a Duke Nukem-style coup de grace.
The shoulder bash ends up effectively 1-shotting anything that's not behemoth-sized. Feels really good to blow mechs apart using the power of robot martial arts. Only problem is that enemies are generally too agile to land the shoulder bash consistently. Eventually figured out an elaborate combo that combined an M. Bison Psycho Crusher granted by claw arms, laser beam sidearm OTG and air kicks to reliably hitconfirm the shoulder bash thanks to FIGHTING GAME AUTISM.