Thanks for the feedback!
There is going to be an in-universe reason for the player being chosen as the lead role, but I didn't really think of explaining it in the submission. Maybe I'll add some sort of cutscene in the end of the mission to give a hint about the reason.
The alchemy theme was going to be incorporated by adding the option to assign different team members for story progression, but I ran out of time to implement it. I will be working on adding that once the judgment period is finished.
As for those scenarios where you can't go back, I guess you mean the "Work in Progress" dialog? I guess I should have made it so the player returns to the base instead of the main menu. I guess that's on my part XD