I was thinking of keeping them more true to their characters, but just in different positions.
Lydia could be the ancient demon with reality bending powers, who perhaps ran away from the Netherworld because her father, big wig of the demon council, Charles, is marrying Delia. Lydia isn't over her mother's (another demon) death by sandworm, and resents her dad and Delia for moving on so quickly.
When her dad finds out she's run off to the living world, he gets mad and curses her with the name curse so she can't get too out of hand. But Lydia figures she'll find some dumb human to say her name.
Enter some dumb human: Lawrence Betelgeuse. His father recently died, and his shitty mom won't leave him alone. He owns a used car lot, makes gimmicky commercials, and is probably clinically depressed. And also clairvoyant.
Lyds gets intel that the Maitlands are gonna die soon, so she stakes out their house, thinking she can trick the labradoodles into getting BJ to summon her. When the Maitlands' die, BJ, who moves into their house (cheap because they died in it!), is accosted by the not-so-scary Maitland ghosts, and the somewhat scary Lydia demon.
Thoughts?