I think the projectile weapons(rifle, shotgun, chaingun), can use ammo packs, same in function and limitations as battery packs for energy weapons. Ammo packs can increase either the each magazine capacity or the number of reloads (but keep the same magazine capacity), depending on the weapon.
Ammo/poison share is what the name suggests. If your teammate is out of ammo, and you have the same weapon with ammo, you can share your ammo with him. This could be useful during SD and the armory or the reactor is destroyed. For the aliens, you can get poison from your teammate by touching the poison boosted teammate. Some limitations may have to be implemented I guess. Such as reducing the effective time of the poison boosted state.
What do you think? Doable? Good/Bad Idea?