Let me put it to you this way. Percherons are the ONLY animal you will find at Disneyland. They are calm enough to pull the trollys day in and day out. As a breed they are not flighty.
High strung horses like Arabs and TB have the
run far away from danger as fast as you can mentality. My mare was 1/2 TB, 1/4 saddlebred and 1/4 arab, so I've experienced the bolting too. Not fun, especially when it's under trees and you only have a halter and lead rope (hey, I was a kid, I wasn't always a SMART kid!) Drafts, on the other hand KNOW they are big and cannot run away as far and as fast. When spooked, they usually will run a few steps, and then turn around to assess the situation (snorting the whole time!).
So the spooking aspect is different than what you are used to. Could he spook and you end up on your butt on the ground? Yup!
I used to ride a big old barrel chested paint. He felt like a draft, big and round -- but he wasn't. He'd catch something out of the corner of his eye, jump to one side and turn and look at it straight on and snort at it. If you happened to slip and fall, he might turn and snort at you too! I rode him bareback, so I've fallen off more times than I would like to admit when he did that! We did everything we could to desensitize him. He was just hyper aware and always spooky. He wasn't a horse for a beginner, but he was a lot of fun most of the time. We just had to be aware of that aspect of him and remain calm ourselves. When someone rode him that was bothered by him being spooky it was worse. When I rode him (and laughed at him when he'd crow hop to the side) he didn't do it so much. So a lot depends on the rider's confidence and the horse's trust in the rider.
As for riding him in a halter. As mentioned above, I've ridden many horses in nothing but a halter and lead -- again, adult here saying not the smartest thing we did. We had 300 horses and 600+ acres of pasture -- we would often grab a horse that was near the gate and ride out to find the main herd with nothing but a halter and lead, and then ride back down the same way. In the upper pasture that had no trees to speak of it was seldom a problem. Lower pasture had a stream with trees on both sides.
I didn't see anything about him not being ridden with a bit -- just that he COULD be ridden with a halter. I'm of the opinion that you should use the least amount of force necessary. Every colt I worked I started in a bosal. I've worked with almost every type of western bit (and some english) out there. I learned what is termed the Vaquero method and also rode in shows with a spade bit horse. Mind you, most of the time, that horse could be ridden in a light bosal with perfect control. So it comes down to respect and training. I was lucky and didn't even know it back then. I learned a lot of what is now considered "advanced training" techniques when I was just a kid. The term horse whisperer was not commonly known and yet many of those techniques are what I was taught and what I used.
I just hope when I get another horse, I can remember it all!!!
I still say your best bet is go see him. Drop something, shake a hankerchief or crumple up some paper to see how he responds. Is he being Jumpy cautious? Or Jumpy scared? Big difference.
I do have to say, he's an awfully handsome fellow, I can see the appeal!