Well, today I found a picture concerning Chapter 1 of Season 2 (right).
So, here is what I think is the order of Bosses in Mission 1:
1.1: Does not match any Bosses currently in-game, but is most likely Sugar Man.
1.2: Unknown. Blizzard?
1.3: The Boss appears to be Dragoness.
1.4: The Boss looks akin to Vulture.
1.5: Does not match any Bosses in-game, but it is most likely Selene.
1.6: The Hero required for the Premium Mission isGambit (confirmed), and the Boss appears to be Fixer.
This is all that I could figure out from the picture about Chapter 1, Season 2.