More power to you! I feel for you with the dreaded gaited horse trot! My MFT mix would transition into and out of it like a plane stalling and landing with a flat tire, ha ha. I would suggest starting the bridleless training with a bit and bridle on your horse, but only pick up on the reins to ask for collection, and to remind him to remain in and refine a collected frame, while steering with your legs and a neck rope, driving the collection from behind. I'm not terribly familiar with Stacey Westfall's training, but that is how I would approach your collection issue. You can also use the bridle to cue your horse to gait. When you minimally have to use the bridle to refine and perfect, try moving to a halter with reins or 2 lead ropes, the idea being to back from mouth cues to face cues to sheer habitual collection or perhaps a vocal or neck rope cue. If your horse collects really well now, it shouldn't be too difficult to use the bit only to reinforce the collected frame. Even if you still have to touch the reins for gaiting or collection, and steer by the neck rope, that's still a heck of an achievement! If the gaiting bridleless doesn't work out, I rode rising trot on my MFT mix for a long time. The roughness of the trot made it easy to post, if not impossible to sit
! I've never heard of a gaited horse going bridleless, but that doesn't mean it can't be done! Good luck!