My one and only concept for a Twelfth Night adaptation is that Orsino was in love with Olivia's brother, not Olivia herself. I think it would be fun to bring out the theme of substitution (Sebastian for Viola in Olivia's case, and in some ways, Viola for Cesario in Orsino's) It would also bring out the grief/mourning/ghosts aspect more to the forefront: Orsino is pursuing Olivia only because she reminds him of her brother.

Also Malvolio should be a woman