This is a promising initiative, bravo! Having all disciplines in one place could bring together a critical mass such that sponsorship and web-tv coverage is possible, bringing the event more prominence than individual competitions.
I would like to propose another aspect to the event, a competition where young riders (age 18-21) are in the saddle of young horses. In my discipline, dressage, the young rider program is focused entirely on the FEI level and the majority of competitors' mounts are purchased already trained for that level of competition. This is essentially the only way for a talented young rider who would like to enter the professional dressage ranks to gain national prominence. The consequence is that we are seriously lacking in young dressage trainers who have been taught how to start young horses and bring them up for the first 3 years. Showing a trained FEI horse does not provide these skills. Having a national competition of young riders riding 4, 5, and 6 year old dressage horses would address this problem. It would also be more inclusive of a broader range of families because the purchase price of a fabulous 2 or 3 year old prospect who would be competitive nationally is 1/3 to 1/2 that of a young rider FEI horse.
Young riders need their time to learn to ride, young horses need old pro's to teach them, some wisdom already shared some 2,000 years ago by Xenophon. The education of young horses is seriously faltering, there are no systems and is very individualistic (especially in the USA.) We all can not afford more poorly trained nor bred horses, the industry is drowning.........
Learning how to train a young horse by riding young horses unsupervised is not a good idea. Where does one go to be trained to train young horses?