This. Right here.
Michiko is going to be the centerpoint of our second plot thread. Donovan and Viatrix are very much tertiary characters (by choice of the players, no less).
Hence, Cover 1 is Sayaka, Cover 2 is Michiko. Once we've reached the point of needing covers 3-onward, we should hopefully have a better idea of what's coming ahead. Hence, we can plan further covers.