WhatzUp,
The Clydesdale/TB crosses and the Percheron/TB crosses that came to mind were back in the sixties in Michigan and they were being used in open jumping. They negotiated some five and six foot and higher courses easily without soundness issues. I did not follow their careers closley and I don’t remember their names, but several of them were well excepted as top money-making showjumpers and people were breeding more and more of them. There were a number that were being bred back to thoroughbreds. Very nice horses.
I have seen them used in top showjumping barns as high quality school horses. I do mean high quality. Practicing over six feet consistently and reliably.
I saw similar breeding in Austin TX when some people moved out from Maryland and brought their Percheron/TB horses with them. I love the Perceron/TB crosses. We called them Thorcherons. I thought that was a fairly common name for them. Those particular horses had been bred for jumping, but the owner decided to begin taking dressage seriously and there was no big problem with the switch. They were athletic.
I agree that showjumpers and high level dressage horses need to have pretty much the same conformation.
A lot of the modern WB rage has taken the spotlight recently, but a very large number of those WBs have genetic problems bred into certain lines. They do not stay sound. Those are specific lines.
Good bone structure comes in a number of breeds and grade horses.
Many horses that are bred for specific disciplines are not all that great.