So in the end, did the collaboration add anything to the plot or world building of Chrono Cross? Or is it simply a bunch of "What if Kid interacted with Another Eden characters?" type of stuff?
It's hard to say. It mostly worked like previous collaborations in that it's basically "Characters from Collab end up in the Another Eden world, get involved in an adventure similar to their series of origin, then leave."
Complex Dreams, however, does make what could be considered a big change: Harle comes to accept she doesn't have to rejoin the Dragon God. That could have repercussions if she were to return to her world. Considering that the Cross characters have yet to return home, unlike the other collab characters, and that Complex Dreams ends with possible plot hooks, it's very likely this isn't over.
That said, even with Harle having made such a decision, we can't be sure it will stick, since so far previous collaborations also had their characters mostly forget what happened during their stay in Another Eden, so only time will tell if the Cross characters will have the same happen to them or not.
