Yeah, that would be pretty cool with a fixed set of weapons - then you could have a holster for the pistol, a rifle could be slung over the shoulder. Depends how realistic you want it.
When I was doing this, I made a base arm set and added that with every weapon. I had animations for the gun going out of the screen and back in again, so when swapping weapons the hands move away, and reappear with the new gun. That might be a good option if your planning on using lots of weapons - I mean, if you have 10 different weapons, having all of them as a single model would probably drag performance down (what with animation frames and limbs) - you might not even be able to have that many limbs without issues.
Personally, I liked having each weapon with it's own animations, because it's then possible to try and mimic how the gun works in real life, how you reload it, how it moves when fired, how it ejects shells etc etc. I just had 2 arms, offset to their general location, then positioned and rotated those with the camera. It can be fiddly and time consuming, but it's fun as well and I defy anyone to not go ''WOOHOO!'' once they get their gun and arms working how they want in DBPro.
Health, Ammo, and bacon and eggs!
