Rosebud, you can retrain a TB to Western cues, wear Western tack and teach him to neck rein. There's no reason why you can't have him retrained for pleasure trail riding.
As long as he has the right attitude for a trail horse, it doesn't matter what tack you put on him. And yes, some professional training is in order for him to learn how not
to be a race horse.
My TB is being retrained as my foxhunter. He definitely has the build for it and I think he's going to enjoy it immensely.
My biggest issue with him is getting him to go faster than a trot. His philosophy on life is, "Why run when I can trot, and why trot if I can walk? We'll get there eventually......"
There's no wonder he didn't make it as a race horse!