Forget the m4 mag converter, it looks ridiculous.
As for mosfets, you could but to be honest so long ass you're on a 7.4 lipo you shouldn't need one- good choice on the charger, the B6 is very good.
Stocks post a bit more of an issue as there's not much choice for g36s, WE make one called the IDZ, so that's one option. The other is an m4 stock adapter but it looks out of place so wouldn't be my choice.