I was thinking recently about different ideas for season 2, even if there is no official renewal.
My idea was the show's creators to write a series of novels that would be sequels to the series. In my opinion, Eoghan O'Donnell and Trey Callaway should think about it.
A few characters might come with second chances.
The revelation about Amy being the Antichrist changes everything the Messsengers (especially Erin) have thought about her.
And Michael will learn about his destiny.
See also: "If there was a Season Two" by MissVampy13