I'd imagine also Crispin and Amarys, if you're going to show two members of the BB League might as well show off all four.
There's also Cyrano and Briar. Now Briar will likely be the reason why they go to Blueberry Academy, they had called her to ask a question about using Pagogo's power to get rid of the Laquium but she was busy with her book at the moment so would call them back when she had the time. So she'll probably tell them to visit her in Blueberry Academy where they could also get some training. Cyrano is a toss-up as him appearing would just be for a cameo.
Now the real question is, what about Carmine and Kieran? Carmine had made an appearance but it was more just a cameo as focus than shifted to Briar, though she said she was a student of Briar's. If they want to set up the Kieran story as a side plot this would be the time to do it. I can see them making the "current" BB League having Drayton the Champion and Carmine being the 4th EF member before Crispin; Kieran would also be part of the League Club though be is Teal Mask-self. Kieran will befriend the Rising Volt Tacklers, likely start looking up to Roy specifically. Before the end of the BB arc they'd go to Kitikami, probably cause the Countryside Harvest Festival is occurring again and Kieran would of course invite them, where a truncated version of the Teal Mask story will play out. In the end, Ogerpon will want to join up with the Rising Volt Tacklers, and in the final episode of the BB arc, as the Rising Volt Tacklers leave (with Ogerpon now part of the crew), we'd get the scene of an angry Kieran swearing he'll become stronger. Then we'll put that all to the side for the main plot to advance until an evitable return to Blueberry Academy would reveal a shake up had happened with the League Club...
