I hit a button and it deleted what I was writing so I'll just summarize it;
People who really want to be LMG gunners, will adapt to the new rules
People who want uber guns with lots of ammo, will buy a different gun or go play on a field not under MAA rules and regs.
It's just the fact they bought the gun to get around ammo restrictions with no intention of ever using is as a support or assault weapon.
In a way it's helping everybody, since everyone who bought an M249 for a non-milsim reason has a field to play at where they are welcome, and the MAA can stay milsim