alright. got a lot of stuff to reply to. i'll start with this one.
so the guy using the human powered helicopter was both an olympic power lifter and an olympic marathoner?
a strength of 20 is superhuman. we are talking about a level of strength that isn't even possible in the real world without steroids, extensive training, or both.
@dragon flight. nope. their flight is a natural ability. no magic involved, just big muscles and big wings. and they most certainly are not shaped for flight.
@plausibility. it's exactly as plausible as anything else in this game. no one complains when trolls regenerate their head and all their limbs within a few minutes, get them cut off again, and repeat the process.
@graft. that's still magic. grafts are magic items, created by casters.
@critical fumble. this is a houserule. they aren't a thing in the actual rules, or in any game you'd see me in. the closest i ever get to that is a 1 ends your turn, which doesn't interfere with this feat.
@ improved disarm. go ahead, i dare you to try to take a 2 handed weapon from someone strong enough to fly with it. waste the action, please. besides, what's 10d6 max falling damage, anyway?
@sunder a good DM won't remind the players about how to destroy other players' gear, nor will they go around looking for ways to screw their players. and no one said the weapon wasn't magic. legacy items FTW. no caster needed for that.
@dragons again. well, personal houserules really don't matter here. dragons can attack with their wings while flying. and no, they can't attack while gliding. gliding requires holding the wing out straight to catch the air, you can't glide if you're moving your wing around trying to hit someone, because the wing isn't catching air like that. it has to be done as part of the flapping motion.
@hold person. yep. you are in the same danger as everyone else using any non-magical means of flight. a bird has the exact same problem.