I might be wrong but, I'm pretty sure we're missing a whole bunch of Gunslash weapons (and other weapons too) that aren't in the drop tables just yet. Itsuki's Gunslash (Nagerling?) is apparently a rare drop from Banser Ong according to the Arks-Visiphone, but there's no sign of it in-game.
So it'd definitely be nice to see both weapon camos & missing weapons be added eventually.