Being a big fan of gym leaders in general, I have a feeling that I'm going to love this new feature. I think it will have some post-game longevity because in each tournament you're only facing a certain number of leaders/champions, so in order to face all the available characters you're gonna need to run through it again.
I hope that they keep it on a certain day of the week instead of being able to do it whenever you because it would make more sense in the game and it would give me something to look forward to every week. I don't know, just an idea.
Either way, this will be a great addition to the game! :D