My philosophy starts with that a horse knows how to be a horse…you cannot impose anything on a horse…it has to come from and be offered by the horse. So see what you have before embarking on any program.
Draft horses were bred for pulling. Ergo, they lean into the collar or the breastplate which puts them on the forehand.
With that said, one of the best piaffe’s I’ve seen came from a Belgian that was a former Amish plow horse.
My suggestion is to go ahead and see if you can see your horse at liberty…see how it moves. Perhaps a precursor, is to start to develop the language so that you can ask the horse to stop and turn.
See how the horse behaves with it’s own god-given abilities without a rider on its back when asked to canter and make changes in direction. This has to be a controlled affair…NOT just chasing the horse in a pen.
I went to see a prospect at a major breeding/training location that everyone here would know. The horse was free-schooled in the indoor…gave a beautiful gaboingy trot…BUT…when asked to canter, it cantered down the long side but once it got into the corner it did not have the innate sense of balance to shift its weight backwards, engage the inside hind, and make the turn on the short side without breaking into a trot.
As a starter exercise, I would start with walk-canter-walk…if you have that ok. come back to talk.
You will probably see that the first few strides of canter are light and get progressively heavier…Do NOT canter more than a stride or two before asking for the walk. Ask for the horse to walk…keep the horse in a collected walk… and then reward.
Get the horse to understand that you want only a few strides of canter and pretty soon it will start to expect the walk transition and maintain its own collection. This is how the horse offers collection. It does NOT come from the rider.