I'm really impressed that you managed to submit a full game design document and you have a well thought-out production plan. The being said, the scope of this project seems to be a bit ambitious for the amount of time you have for production, so I might scale down a bit on the complexity of the mechanics. I really like the examples of the cell-shaded aesthetics that you want to use! I would take another look at your color palette and how you can use color theory to convey negative/positive changes in the environment as time progresses in the game.