Okay this looks more and more like Final Fantsy X-2...
Defeat Lightning in the coliseum to make her a party member? They did the same thing with Tidus, Auron, Seymour andShinra in X-2 International, as well as the whole idea of putting monsters in your party instead of having your party get more human members through storyline. Also, the whole "explore all the timelines" instead of following a set path throughout the story reminds me of X-2 as well. Besides, they're going to release "episodes"? The only thing missing now is being able to feed your monsters items and accessoires to strengthen them.