Before I begin I would like to tell you that I have no hatred towards the Ghostforce series and that this is just an opinion related to Miraculous.
In my opinion, creating Ghostforce didn't seem very useful because in the end we could have had something much better and here are the two ideas I had and given the nature of this series which takes place in NY, they will have a link with the Native American Miracle Box:
1) Make sure that Andy, Liv and Mike are the holders who belong to this box - What I mean by that is that instead of making it so that Jess gets the one from the eagle, I had the idea that this Liv (with Andy/Thunderbird and Mike/Bear or Buffalo). We could have seen a whole new trio that could use them against the ghosts (I'm using these villains here because they're the ones from Ghostforce but it could be anything/whoever else). This would also allow them to connect to the Miraculous universe (or at least the Quantic Universe) especially since we still don't know if they are or not.
2) Abandoning the idea of the Ghostforce and instead making a series focused on Eagle and her future team - Instead of creating a series like that they could have taken the opportunity to create a spin off on it and this will have allowed us to know all the Miraculous present (same for the proposition above) as well as more characters.
Tell me what you think about it!