I disagree.. If he did dressage, he'd be fine. Hunters would require shorter stirrups and jumping too. He could (if he wanted to) manage English just fine. The trend is taller horses though, but honestly shorter ones can do English just as well :P
I didn't say he couldn't do dressage with his current horse. I just said if he wanted the "look" - and can you really disagree that the current trend in dressage is towards taller horses? Now me personally, nothing is more beautiful than a smartly put out haflinger doing passage.