Donny Burns is one of the biggest legends in ballroom dancing and would certainly give brilliant, constructive comments.
I doubt he could do it though. He judges many competitions, he teaches many of the top pros and he is one of the top people on the World Dance Council and International Dancesport...I think, or is he head of the competing organisation??..he's got one of the top positions in dancesport anyway, which I would presume takes up a lot of his time. I just can't imagine that he could fit in Strictly and he may not wish to either, as he is so focused on the competitive circuit. He would certainly be a fantastic addition to the show if they could ever get him though.
Paul Killick would be an outspoken choice and would be great, as he knows more about ballroom dancing than Bruno, Arlene and Craig combined. However, again, he already has a career that is very much focused on the pro circuit. He teaches and I believe he may be coming back from retirement to compete again.