If the weights in the ammo cases varied there would be even more strategy. Like Hades said, if there were "match-grade" ammo cases and "grunt-grade"(lol?) ammo, ie .36 and .25. Obviously sniper resupplies will need to be cut down as there will be much more grunts around. I do really like the idea of ammo control, that's nuts.
I can see the need for .36 in BA's, but regular shooters should be getting .25's