NIGHT OF THE LIVING DEAD:
It would be really cool if on the Halloween SO the recruitable hero would be Blade, and a villain would be Morbius the Living Vampire, who could be later on recruited by lockboxes and thus creating the Midnight Sons. I mean we already has Dr. Strange, Daimon and Ghost Rider and we need more of those supernatural and demonic heroes and villains. I think it really fits on the occasion too. The goons could be vampires etc. It would be fun I guess.
Mission 1 could have ghoul minions, maybe redesigned Maggia goons and the boss could be Deacon Frost with Blade Team-Up. Mission 2 vampires with Dr. Voodoo Team-Up (not boss T-U), the boss Morbius the Living Vampire (in the conversation before the fight he could be arguing that he's not the one doing this but Blade does not believe him or something). Mission 3 vampires, the boss Lilith with Morbius Team-Up and epic boss Dracula with Blade Team-Up. I haven't thought about mini-bosses, and we all know that they won't do more than 4 new villains for the SpecOps.