Basically, I came up with a spectacular "what if" scenario.
What if the Chrono Cross ended up merging every reality instead of just one? Think about it, a literally infinite number of universes including ours merged into an infinitely large omniverse.
The story would pick up where Chrono Cross left off, with the live-action Schala in what appears to be Tokyo. She speaks directly to the player, telling him/her that he or she is the only one who can save reality from certain destruction. She then uses her amulet to open a gate that leads to a yet unknown time and place.
The main cast of Chrono Trigger is back again for this one, only it's eventually revealed that they're actually each from different universes where events happened differently. Crono, Lucca (from a universe where she didn't die), Marle, and the others, find their way into space somehow, visiting many different worlds.
They soon discover that there are an infinite number of worlds out in space, and they realize that the Chrono Cross must have merged them all somehow.
Naturally, merging infinite realities into one creates an enormous distortion, and that distortion threatens to destroy all reality, a goal that the main villain (whom I've yet to come up with) seeks to accomplish. This is also implied that this will erase the player from existence too, breaking the fourth wall in a sense.
In the end of the game, Crono and company, along with quite a few new faces (whom I've also yet to come up with) from alternate realities, head towards the distortion to find the titular Chrono Break, which acts as a sort of reverse Chrono Cross, as rather than crossing all the realities into one, it breaks the one reality into the infinite realities that the omniverse was before. The player quite literally reaches through the fourth wall to guide the party as they seek to prevent the distortion from destroying everything.
In the end, the party fights an unwinnable battle, and the final boss, the main villain merged with the distortion's core, wipes the floor with the party in one turn.
Just when all seems lost, however, Schala appears again, revealing that she was the true Chrono Break all along, and sacrifices herself to separate the player's universe from the omniverse, but is too late to prevent every other universe from being wiped from reality.
... Until after the end credits, where it's revealed that the player's memories of the game are enough to bring back the other realities to the way they were before the Chrono Cross was activated. It is also implied that the events of the game will happen over and over again in an infinite loop.
