>>56411280>Can Decomp Emerald be made 3v3?so I looked into this a little while ago. it is believed to be possible, but not currently implemented, so you would have to code it from scratch.
there were plans to incorporate it into the decomp at some point but they got shelved indefinitely because I guess the amount of work was deemed not worth it for now. the biggest hurdle would probably be visually, it would be tough to fit all those sprites on the GBA and you would probably have to redo the entire battle UI and make a lot of changes to move animations as well.
I seen picrel, I believe this is just a wip that somebody is working on in private. but it shows that it's possible, although they changed the entire UI here to be like classic rpgs.
so if you're willing to do it yourself from scratch you can probably implement it, otherwise I would wait a few years and keep an eye on the pokeemerald-expansion updates, maybe they'll come back around to it in a future version.