Nah, running out of ammo is not the problem. The problem is how FAST that happens and after that you have exactly two choices: run into the enemy, trying to TAG as many of them as possible (or if you don't have a TAG, hope your side hears your screams of enemy positions) or step in the line of fire to give someone else time to reload a cannon or cool down.
In MW3 you had the mobile repair post which could refill your coolant (coolant flush wasn't a one-time use there but simply dumping the heated liquid to fast cool in exchange for worse cooling later) and restock your ammo. It took you out of a fight for quite a while and when it was damaged it was lost so it needed extra care and distance to the front lines.
Something along that would be nice here, too. But then, maybe I'm only caught in the triangle of weapons/speed/armor and want to have too much of all three