Think about it.
Missions would be based on the characters.
5 Characters start off with, until you gain access to Ax.
Story line follows the books.
Like, Jake's first morph to a Lizard, trying to run away from the light and getting stomped on. Or when morphed to ****roach. Invading the Yeerk Pool.
Once you reach the part where the Yeerks discover that that Andidate Bandits were humans, you will uncover a mode where you are being hunted by the Yeerks in full out police chase/bug fighters/Visser One, etc.
And of course, the tragic ending. Of course, I would end the story at the end of the tragic ending, and show casing what happen to everyone else and how happy they were with Jake being told he gets the ability to fight again. And end it on that.