Herman is a reanimated corpse, and his wife Lily and Father in Law Grandpa are Vampires, what could possibly be a suitable setting for Fuller's preferred themes of Life and Death if this doesn't qualify as suitable? Marilyn can't get a second date, because her family scares the men off, sounds like a very suitable setting for unrequited love to me
In Fuller's previous work, "death" is finally growing up and understanding that life is the mundane stuff you do every day and "life" is what meaning that mundane stuff creates for you, in opposition to the meaningless of death. B'Elanna Torres in Barge of the Dead has an epiphany about the heroism of engineering (amongst other things,) and George in Dead Like Me actually gets a job to support herself (and keeps having weekly maturing experiences) and Chuck in Pushing Daisies is compelled to get back in some way to her mundane life with her aunts.
Symbols of illicit sexuality like vampires are not a natural fit for this kind of oeuvre. "Herman" might be if he remembered his past life/lives (?) and didn't love Lily but I'm pretty sure the formula won't be tampered with so much. As for Marilyn's unrequited loves, she only has to move out of the house. There's no drama there, and the humor is the laugh at the idiot kind.
Oh Fuller is talented and he has more than his preferred themes so he might make this fly. But maybe not. Humor is conflict. The conflict between being monsters and being a loving family was the essential tension in The Munsters. The essential tension in Mockingbird Lane seems to be the conflict between being monsters and....being unpopular because you're monsters?
This is the motor that's going to propel a show?
Obviously final judgment must be reserved.