The best solution for this would just give Sith something similar to Dark Rage in base. You get speed for the cost of draining health and force. Although I don't know if giving a damage boost would be too op or not.
In my opinion, most people aren't going to need a 600 ammo pool. I find going with ammo 2 or even 1 is enough in open. As for "magazine size" I agree it always depletes when you need it most; but it is a really great weapon as is.