This game sounds like it could have a very compelling narrative and could be jam packed with interesting and unique puzzles. Unfortunately, I think your GDD doesn't really reflect this as concisely or in as much detail as it needs. Thematically I love the idea of warping through time Bill and Ted's Excellent Adventure style, but I don't think that that is quite enough to be a new genre. Your GDD has a lot of unnecessary verbose wording to it, which does make it hard to read. I really think it is a great game idea, but just needs refining and consolidating.