Even though I have never actually had a successful Role-Play, I do suggest you have just a bit more of a wall in this sandbox of yours. What would you classify as a good behavior, what would you count as negative behavior. Also, you have a good base, but from the Role-Plays that I have been in that was halfway successful, they all had an idea of what the end would end up like.
You are just saying that they are going to go for the Elite Four, Gym Leaders, and Grand Festival. Why would they be doing that rather than just wandering around hopelessly. we all know hat the Elite Four has a somewhat good prize, and that is that when you deeat the champion, you become the champion itself. but nowhere have we ever found out the true prize of either of them. Think of the reason they are doing this. To prevent all the pokemon from going away like they did originally, to prevent an organization from destroying the world, or forests, or just for the enjoyment of having the battles. they need something to drive them. You jsut say that they are going for the Grand Festival, and Elite Four, what does that do for them though. why should they train their pokemon for it, and what would their star enemy be.
I am basically saying you need a hook to go for it. Ash didn't go just for the fun of it, he went to catch all teh pokemon, and become the champion. in a game, you wouldn't go just to beat the gyms and elite four, they would have to be extremely weak, they have to have some sort of meat puppet they destroy or lose to constantly.