Besides Legion? I'd say anyone with firearm experience is a good place to start. The profiles should tell us anything like that.

I'm not prepared to narrow the list down past that just yet, but at a glance I don't see anybody else with firearms specifically mentioned. K has augmented strength and Belgium is skilled with "various weapons", but those both could mean a lot of things.

Edea was also marked as VIP, but yesterday she told me she only uses melee weapons and hand-to-hand combat like myself. Her profile seems to confirm that much.