This slot would allow infantry to equip Ammo Belt, Grenade Bandolier,Munitions Pouch (Heavy Assault) and perhaps Utility Pouch (Engineer). These aren't really defensive upgrades and should get their own loadout slot option.
There would need to be more armor options. Not only that, but its pretty balanced as it is. Do you want to be able to take an extra bullet or two, take a mine to the face and live, or throw a few more grenades, or fire a few more rockets? In the case of Medics and Engies, they are trading survivability to specialize in their fields. Medics need to be vulnerable if they are going to be able to toss 4 revive grenades.
Or the the medic could go for flak armor so that he survives what he already does best without the help of good-xp-generators-but-otherwise-not-that-great grenades.
