I don't really like the separate ammo from the weapons, first because there is no real reason to do that actually.. and maybe there are too many situations where it will, like in RO 1, be blocked inside the world and you will not be able to take the ammo, only the weapon. The idea of having multiple grenades on the ground is more interresting.. but it is not really a need I think.
ammo + weapon as 1 oject causes tonns of problems.
For example, if you are a machinegunner or AT rifleman and you see second MG or ATR on the ground, you can only take ammo with destroying weapon. Machine gun or AT rifle is strategically important weapon and this is very important to not loose them, but sometimes you are forced to destroy weapon that could be taken by your comrade because you need ammo.