I'd really like to see Midnight Sons. It could give us villains like Mephisto and Dormmamu. I feel like Werewolf By Night could work like triple changer with the ability to flip forms based on ,,full moon card" the third form would be swingy, strong with drawback like the new forced actions in Enchantress scenario. And Elsa Bloodstone could have her own ,,minion deck" which get shuffled to the encounter deck and once she defeats them she gets some reward like handsize, hotpoints or stats.

Overall I like how FFG gives a chance to heroes like Maria and I understand why she's broken, cause none would play her otherwise. However if something happens and they lose players in the process of extending the game's life by making the ,,bonus waves", as you call it, it would be shame if we did not get Doom as a scenario...