Ok, I see your points, but the if the weapon would refill on being picked up, all you would have to do is have another team mate with you and then its basically the same as it is right now
also, if it was refillable by !ammo, then its also basically the same as it is now
perhaps a good compromise would be to refill at building terminals, or possibly refill tanks (to give them a use) which would also limit the "fly to high position and camp for a whole game" strat.
I remember a game a while ago, I played on the map with kirovs (forgot the name) and someone camped gdi base the entire match with AGT gun from the center cliff, and after they killed the kirovs, I had no way to get to them or kill them from the ground, it completely ruined the game