I don't think you should let people choose their loadouts.
It's difficult for me to explain why, but I think it's just... lame.
Giving people specific tools to use for specific jobs (by use of specific loadouts) will simplify things.
Plus, every DM I've been to where you've been allowed to choose whatever weapon you want for yourself was just nasty-bad, and there was no consistency.
If everyone can choose their own stuff, then you don't know what you're up against and can just wind up getting your ass kicked every time because there's nothing to go off of.
If you have specific loadouts set up (heavy, scout, sniper, etc.) people can use different strategies to be victorious. That's all I'm sayin'.