It depends on how it's laid out, you say for 15 guns it's too much work, I'd agree with that if your talking about completely redrawing this stuff. But, if it's a specific area of the texture that holds the hand stuff, then things are a lot easier, just have this part of the image as a new layer on each texture.
Really, I'd expect to see the hands as seperate textures, like you'd have 1 single hand texture, easy to change, easy to adapt - and changing this one texture changes it for all the weapons.
Perhaps it will be quite complex in FPSC, in DBPro I'd probably have 2 complete sets of weapons, one set of weapons per hand texture - wasteful, but in DBPro you can't retexture bones, so you have to texture everything in the animation proggie.
