There were two unproduced 'Beetlejuice' sequel scripts floating around the ether in the '90s; 'Beetlejuice Goes Hawaiian' being one of them, and another being 'Beetlejuice in Love'. If I recall correctly, It was set in the middle ages and was about a playwright who dies and gets sent to the Netherworld, where he would enlist the help of Beetlejuice to get him back to the land of the living.
I read it many years ago and I honestly thought it was pretty decent. It obviously features none of the original cast sans Keaton, but I think that's a good idea. The story of the Deetzes and the Maitlands has been told...you can't really go anywhere further with those characters. It's better to simply focus on Beetlejuice, the irrefutable star of the show; for a character several centuries old, you can't tell me you can't write an original story for him without drudging up the original again.