How about this: Wait until you're 17, kid. It's M for a reason.
I find it odd that a someone would request, on a game that's supposedly modern and realistic, an option that takes out the most realistic things...
While we're at it, why don't we make Ghost Recon: Future Soldier a NERF game? You can shoot big rubber darts and have every enemy wear neon yellow targets...
...because that's what you're asking.
Better yet, just play a NERF-branded game. You get no blood, no language, you can get your shooting jollies AND it's not M for Mature.