How about the American Saddlebred for dressage? Anybody doing dressage with their AS? :)
There are a few. https://www.youtube.com/watch?v=IRpjVbiUIAA
I think another thing to consider when talking about "which breed for dressage" is what is the riders ultimate goal? How many riders that ride dressage go all the way? Often, it isn't the horse that holds them back, it is the rider. Many riders do not wish to commit the time, patience, money to going to the top. Many riders are thrilled to do first or second level and many breeds are more then capable of doing that.
I have witnessed so many extrordinary horses that are being ridden by people that hold the horse back and then riders that do not have the horse to take them as far as they could go. Sad that we couldn't just do a bit of horse swapping.
I personally think there are tons of Saddlebreds that could climb through the levels easily enough but few people think of them as the "breed for the job" many see them as a park horse and that is the totality of their ability. People who have tried them in other disciplines are often shocked and happy with the actual diversity these horses are capable of.
Thoroughbreds can be great horses too. There are some that are competing successfully at higher levels and some that would struggle in the lower levels. Chosing the right horse for what you want is the key and being honest with your own abilities and limitations. Why have a $40,000 + horse if you will never go beyond the lower levels. I mean, if you like that particular horse, and can afford it, go for it but it takes a team to truly compete at the higher levels, the horse can't do it all by itself.
This is a Thoroughbred off the track. https://www.youtube.com/watch?v=Sx8IFlknNIU
Silva Martin wanted to show people how these horses CAN be retrained to do other things. Playing the "call to post" in the beginning to show that the horse doesn't fly off the handle just from old memories. I love that horse too.
I tend to be a "root for the underdog" type person. I love seeing people who are willing to put in the work and take up the challenge of the less common breeds in a discipline and still succeed.
I wanted to add this quote from someone else, mostly as I agree 100% with it. Ha ha
Dr. Deb Bennett, PhD., analyzed the American Saddlebred in her Applied Conformation series (in Equus 225)
"For more than 100 years, American Saddlebreds have been produced for the purpose of carrying a riders weight comfortably and efficientlyI have never seen any Saddlebred horse - even a part bred - who did not readily perform the passage Most have incredibly comfortable and coordinated canters as well I think they are the most neglected of all breeds suitable for dressage."