That's not how discharge ratings work.
If you can use an 11.1, doesn't matter if it's 25C or 6000C.
If they're telling you to use a lower C rating to choke the amperage going to the motor, then they're fucking retarded because that's how you get your house burned down while charging a lipo. Over-current draw (drawing more current than the lipo can supply) will damage the lipo and potentially set it on fire IN your gun.
If the mosfets shorts out, just get a tougher mosfet.