What if they made a couple of animations for weapon slings (over the shoulder sling, across the back sling, under the arm sling, etc.) and just swapped out the weapon model? That way, they could re-use the same animation, instead of having to create a separate animation for each weapon.
Example:
You have a under-shoulder tactial sling, so you can conceal your weapon under your trenchcoat. In that slot, you can then choose whether to carry your SMG, your shotgun, or your bullpup caseless assault rifle. The animation for drawing the weapon would remain the same (or virtually identical, if your shotgun doesn't have a pistol grip.)
/edit
Riffing off Wisdom's idea, if you had a hip or thigh holster, the drawing animation would be the same, for the same weapon class. Any Pistol in a hip or thigh holster would use the same animation to draw the weapon.
Revisiting this idea. Along with set weapon drawing animations, I propose four weapon slots:
1. Melee. This could be your knife, brass knuckles, collapsible baton, or other close n' personal item. Smaller items could use the same weapon draw animation. Larger weapons (katana, baseball bat, sledgehammer, etc.) would have their own animations.
2. Pistol. Again, the animation for drawing the weapon would remain the same; the weapon model would just be swapped out.
3. Tactical sling weapon. This could be your SMG, your PDW, your bullpup assault rifle, your shotgun, etc. This is when trenchcoats and concealibility ratings really start coming in to play.
4. Weapon slung over your back. This could be for your REALLY big weapons that aren't otherwise concealable (sniper rifle, RPG, Stinger missile launcher, etc.)
Along with the four hotkey slots, you could carry a backpack / duffel bag / briefcase / etc. for other gear, as necessary (plastic explosive and remote detonator, EMP generator, mines, and so on.)
