Ok people 2 things:
1) IRL in a unit of this sort....(or any military unit for that matter), you don't have the option to carry "anything you want". You don't get to go into an armory like in the 'Matrix' and take however much you want. You are assigned equiptment appropriate to your role with your unit.
2) Imagine the look on your squad leader's face when you are ordered to gear up and fall in and you come dragging ass into formation late because you are loaded down with one of everything, ammo for all of it and 20 nades. Not only would you look like a friggin' moron, you'd probably be subjected to some disciplinary action and ordered to take a psychiatric evaluation. At the least, you'd deserve a good bitch slapping. Not to mention that if your squad became engaged in a fire fight or had to move quickly to or out of an area, no one would wait for your slow ass while you got tangled up in the straps for your M16 deluxe(ACOG/ M203), your MP5sd, and your Robar while trying not to drop your DE, Kabar, 15 different mags with 4 different kinds of ammo. Oh sh*t!! You'll probably expect to be able to fire any of these weapons accurately while running as fast as you can on top of everything else....assuming you can even move. Come on!! Where is the realisticness in that?