It's not the heat that you worry about it's the air! Come on! Everything i said is a basic understanding of science that you should have to graduate highschool (and i'm from the state that is ranked 46th in public education, that however doesn't include higher education). Air is matter so when you move through it you displace it and the faster you go the more air you displace, this process builds friction. Air resistance (which is the friction caused by air displacement) actually limits how fast you can fall, don't believe me, go jump out of a plane.
Do give me some credit, please. I've graduated from college, and I know what I'm talking about. Yes, air resistance slows you down, imposes a maximum gravity-powered falling speed, and is a form of friction. It does not, except possibly at speeds very close to the speed of sound, cause any problem feruchemy cannot overcome with sufficient power.
Air is matter so when you move through it you displace it and the faster you go the more air you displace, this process builds friction. Air resistance (which is the friction caused by air displacement) actually limits how fast you can fall, don't believe me, go jump out of a plane.
And friction is primarily a problem due to the heat it generates. The main concern in designing supersonic jet aircraft is not how to make it strong enough to survive the forces involved, but in how to dissipate the heat generated fast enough.
If you were to go supersonic it would be like running into a never ending wall and the pressure would kill you move or less instantely.
No, that's what happens
at the speed of sound. If you go
faster than sound, you leave the "wall" behind.
Regardless, a feruchemist would not have to move supersonic in order to beat a mistborn. All you need is enough speed to make aiming at you practically impossible, and to get to the mistborn before he can dodge.
And different parts of your body take years to heal, according to my Genetics textbook nerve cells gennerally take 5 years, (and some organs/ bones only refill with scar tissue while others don't heal) a head shot would kill you period.
If a headshot actually hits and gets through the skull to do major damage to the brain, then yes the feruchemist is dead. As for speed of healing other things, consider a) Sazed's encounter with Marsh and how he handled the rings Marsh embedded in his belly, and b) Marsh after Vin got through with him just before ascending. Following those examples, a year or two of stored health would be enough to heal almost anything not instantly fatal, I think.
And anyone who works out with any fitness guru or a bunch of football players will tell you that people who lift more than their tendons can take end up tearing their tendons which has nothing to do with muscular strength.
Ok. What makes you think tapping a pewtermind doesn't increase tendon strength too? Again, if this were as serious a problem as you seem to be advocating, I doubt the boulder-tossing feat described in Alendi's logbook or Sazed's fight against the Koloss would have been possible.
In FE Vin explains on her first pewter run why she can run so fast without falling
I'll grant you that tapping a pewtermind probably doesn't duplicate that effect. Tapping mental speed should work to compensate.
And if you try to balance strength with weight it takes more strength to balance the increasing weight
I rather doubt the increased weight would take
all of the increased strength, and you'd only need it during those short moments when you're exerting your strength. When you're just moving around you don't need it, and when you're tearing something apart the increased weight is a lesser problem because you don't actually have to move your body very much.