Go back 8 page, I already wrote on that.
In short, any horse an benifit from dressage work, dressage is training - literally. What I have found is horses that are bred for it, it comes easier to them. The balance, the elastic, suppleness. What you see in a 4 yr old when you first get on one of those “bred for it” is amazing as its just there and you build on it.
When you have those who are not, such as drafts that have straight shoulder, croups and hips that are built for pulling, not elastic quick hind legs, you run into road blocks. Can it be overcome, yes… to a point, but not was easy as the horse that is bred for it that offers. Those that can have a active and quicker hind leg can step up under itself, elevate the front end and give power, which the draft types (as we are talking about) are heavier made in the front, with straighter shoulder (for pulling) and are not quick behind due to conformation.
It comes down to how much you want to work at getting up the levels.
I said before, that many draft and draft crosses would make awesome horses for low level AA’s wanting to go out, drink a beer and just have some fun, but for someone wanting to go as far as possible, I do not recommend that choice. Its a long, hard and expensive road, so why not start with a horse that CAN offer the simple dynamics that will make a trainers and riders life easier.
Re: the registries, I live and breath this stuff cuz of what we do. So it kinda gets to me when I hear goofy stuff that does not makes sense. Its stuff like that, that misleads people and its uncool.