You can hack any game on the Xbox360 but it is even "harder" than writing a simple hack for pc games.
You need a
Flashed Xbox 360 (you can use JungleFlash maybe) -> SoftMod
Knowledge in ASM and Ollydbg.
When your Xbox 360 is flashed, you are able to run 'backups' which is basically pirated games.
You could backup your BF3 on to a DVD disc, and along with that, reverse engineer the game until you are able to alter some of the code to where it gives you an advantage in the game, you then will need to know how to spoof Microsoft's security measures in order to execute your modified libraries/game.
Chances are high that you (they can ban your IP adress) will get banned from Xbox Live for ever, so that's really not worth it.
The code itself is always the same routine, Aimbots use routines like, Bonedetection, Pixeldetection(which is not efficient, cause a game has a lot
of different color pixels) the list can go on, but the structure is the same, the hard thing is to play with a soft modded X360 online,
offline it wouldn't be interesting would it ? :P
I think thread should be moved to Xbox 360 section.