My Crossover fanfic

Hello I said this in another post about story changes now I officially want to write an Fanfic of Miraculous X Bakugan
as said the story takes Place in an alternative Reality And in that universe kwami's miraculous and this stuff dosen't exist and Instead the Kids Have Bakugan's The story Follows Dan and of course His trusty Bakugan Partner Drago and few other characters Who try to Fight against the evil Naga and his elite Havoc
I wanted to ask what Other characters must Be in the fic along side Dan and what attributes should they have
should it be all already Existing characters or no few OCs come to fic too ?
Please don't mark it as an spam