I have a sudden urge to collab that idea with you. o_o
It's not the most original idea, and it's not confusing; a commonly used thing is chapter-switching, where you switch 'team' or 'character' per chapter until when they meet up, when you have a sole narration for all of them.
I'd be happy to collab, if you want to.
Anyway, it's not going to be per chapter. A wonderful example of what I'm trying to accomplish was the previously mentioned
Good Omens, which is a hefty volume of about four ridiculously long chapters ('Thursday' to 'Sunday') which has a bucketload of important characters and switches perspectives remarkably often. Actually, Good Omens was a collaboration too - between Terry Pratchett and Neil Gaiman, but still. The different groups don't meet up too often in this story, which is a lot like what would probably happen in my story - what reason would two groups of Evil Teams have grouping together with a couple of Trainers (and vice-versa) or their mortal enemies?
I don’t see a problem with that many main characters, but it sort of depends how long this story will be. The longer the story, the more room you have to balance them out and develop their characters. Though, having that many main characters is a pretty good idea since it allows you to explore different perspectives on a single issue, so as long as you balance the characters (i.e. give each group their own screen time), you should be fine.
Changing perspectives like that isn’t confusing as long as you don’t change perspectives too often, like in a middle of a scene.
Oh, it will definitely be lengthy, and I do want to explore a lot of the characters' personalities. I wouldn't do it in the middle of a scene, since both Teams are on a lead that the various Orbs are somewhere in the Frontier wilderness and - Mew forbid -
together, and considering the Trainers are Kanto natives and I'm on the fence if the Ranger should be included at all, they have no knowledge of just who these schmucks are (at least one of the two Team groups are smart enough to not tell them), they'll all be working towards the same goal: find the Orbs.