LOL, I have many many disciplines, some with the same horse, some not. The most that I have for one horse is.... Driving, packing, ranch work, cow work, cutting, reining, barrels/other rodeo events, trail, 4-H shows, pleasure, jumping, hunt seat, and we're just starting dressage. haha, so I think as long as you don't sour a horse doing just one thing, and work with them tons, they can become an awesome all-around horse that can do it all. everything that they do benefits all their other events, I think. it might be a little bit of a personal choice, and i understand that people that are going for big time money might just do one thing, but if you were that horse, wouldn't you get bored? My horses actually go downhill if I don't give them a break from each discipline every now and then. Just rotating seems to keep their minds fresh and they seem more curious and excited to go riding. If I were you I would do it all haha. Plus, it's fun!
To rein a horse is not only to guide him,
but also to control his every movement.