Now now, I think PWT counts as a good Battle Facility. I would love for either a Battle Frontier or a Pokemon World Tournament to come back to, as I never beat the BF's when I was younger (because I didn't know what EV training and good team balance was) and I sorta stopped playing when Black 2 came out (I still haven't properly challenged the PWT yet). The main reason I want them to return is because now it's SO easy to EV train, IV Breed, and get good Egg Moves/Abilities/Natures on your Pokemon, and I sure ain't gonna go back to those old games and spend a day training three Pokemon in such a painful way.
With these being the 20th Anniversary games, this is the best time for a return of the PWT. Have our character travel to Unova (only giving us access to at most Driftveil though) and see many of our favourite characters from the old games, many characters from all 20 years gather together again in one place to truly celebrate the anniversary. Perhaps even include Elite 4 members this time, and include more characters like N and maybe the protagonists. Hell, if not that, have something like it in Alola. I'd imagine Alola is a great tourist destination, so why not have old Gym Leaders come visit? I'd imagine we'd at least be getting to see some old faces again, like how we saw Cynthia in B/W.
But the Battle Frontier oh lord, the hours I put into the Emerald one as a kid, and I only got the Silver and Gold medals to the Battle Pike, and nothing else. Shows how much of a scrub I was back then. I think I did a little better in Platinum though!
I really want these to return because if Game Freak aren't going to up the difficulty in the main games, then they should at least bring these back (and put more post game content) for the more experienced battlers. The Battle Maison gets boring after a while. Sure there's always Wifi battling but I'm not always around wifi, and competitive battling can be a headache sometimes.