A large adult in the wild would go 18". I expect a tank raised specimen would stay at or under a foot, but anything's possible. I see a B. dentex and an H. malacabrius as a half-sized analog to the traditional dorado and aimara combo.
As for whether or not the Brycon and the wolf would play nice, that depends on individual personalities. If you go with a mala and a Brycon, I think it could be a good match. If I were of a mind to do this, I wouldn't be afraid to try it.