I couldn't think where to put them all! That's why I opted to get wigs for my Liv dolls and have them double as Jem and the Holograms. Fortunately they'll work if I feel the need for Miraculous Ladybug too. The couple of ML dolls out are pretty good but it wouldn't satisfy us, this is a license that if taken advantage of would produce some nice dolls.
The way the ML movie works is you can watch it if you haven't seen the show but if you do get in to the series it doesn't quite go like that and you'll be in for many pleasant story expanding surprises. If you've seen the show the movie will play out more like what-if fan fiction exploring if some different choices were made.