And while we're at it, they can let us visit a redone version of Emerald's Battle Frontier using this concept, meaning that the Battle Frontier will no longer be a lost concept missing in OR/AS. What they could do is after the champion is beaten, a wormhole is discovered on one of the islands, that just so happens to take the player to Hoenn (original), or more specifically, the Battle Frontier. While we're at it though, they can also let us explore the rest of the original Hoenn! If they do that I will cry.
So obviously as i have mentioned so many times before Battle Frontier is the one feature that I want returned to the Franchise. However reading how you thought they could expand on how to return the Frontier to the Franchise got me thinking about something that I read in another thread that I thought was genius.
So what I read in the other thread was this (I can't remember who posted this idea, but it's a fantastic idea and whoever came up with it deserves full credit):
Battle Frontier can return because of the significant return of Anabel.
Anabel was one of the most important Frontier Brains of the Battle Frontier. She was the Brain of the Battle Tower and besides running the entire Battle Tower it was also heavily implied that she helped create the Battle Frontier as well along with the other Frontier Brains.
In Su/Mo she returns and explains that she was originally the Brain of the Battle Tower but had lost her memories between running the Frontier in Hoenn and having appeared on the Shores of Alola. The Agency she ends up joining finds out that she had disappeared into an Ultra Wormhole during the time involved with the gap in her memories.
Once you have captured and/or rid Alola of all of the dangerous Ultra Beasts, the Police Headquarters gives both Looker and Anabel paid leave until they are to be given further orders for new missions. Considering Anabel chooses at the end of all of this to instead of going home, decides to stay around Alola for an undefined point of time. This could easily be the segue needed to have her establish a new Battle Frontier with possibly new Frontier Brains in Alola.
Game Freak practically set up the background story needed to build a new Battle Frontier already whether intentional or not. I'm not saying that this set up is absolutely confirming that we'll get a new Battle Frontier, but considering how easily they set up a plot line that could easily allow them to insert Battle Frontier without any further explanation necessary, I think that this allows the idea of Battle Frontier returning a realistic possibility. If Game Freak really wanted an excuse to try inserting the Battle Frontier again into a new game, I feel like that USM would be the perfect game to do it in.