I can't let you mimic other peoples quirks while he is attached to them. Simply put that is a bit ridiculous because a lot of people derive from their genes, and even if they don't it ruins individuality of quirks. 

Having an uber charge is too much for a my hero roleplay. Invincibility albeit however briefly it is does through is still invincibility. It gives someone like midnight the free range to do whatever he pleases in that moment. 

75% Must have an upper limit on what it can take. Making them harder to stun. or harder to knock off balance by way of say a punch, or having a desk thrown at them is one thing but a super strength punch, or having a car thrown at them is another.