Not a trainer here - but I've tried fixing a few horses that were what they were when I got them. I learned real quick that I'd ten times rather deal with a horse that's flighty and reactive or hot BUT WILL LISTEN than a rank b-word or sneaky lazy one that blows in two because he's done with the trail we're on an hour in, or worse... the hardhead, temper tantrum pitcher who thinks in a straight line like a bull dozer, no matter the terrain, no matter the trees and brush, and will throw himself down in a walleyed toddler fit when you enforce your will to Not Die on him.
I just off loaded two just like that. Loved Sarge to pieces on the ground - but the ground isn't getting any softer when I get bucked off. Sally was a rude b-word no matter what I did and she was teaching her daughter, Outback, to act the same way around humans. Leroy is the first one I offloaded, a couple of years ago. He was the spoiled huge bulldozer. He was exhausting to ride, nerve wracking and dangerous.
My friend who breeds Streakin Six mares to Dash with Perks, whom I also trail ride, is the same way. She has a foal born to her mares and it's pretty and a good mover, but hard headed and dumb, he or she is out of here. She said she doesn't have time to mess with a horse like that, of any age, and it's not worth risking getting hurt by one in her opinion.
Think I'd stick with the further along in their training horses, tbh.
"We are here to laugh at the odds and live our lives so well that death will tremble to take us."