Delia HAS to be in the third movie, and with a large role. Of course BJ, Lydia, and Astrid have to be there, too. But Delia specifically mentioned haunting Lydia, and I think the idea was to ensure fans she would have a role if #3 happens, and now it is.

I think ghost Delia should sculpt a plaster head for Charles for her own benefit "so that he's easier to look at" (though the bitten-off head was funny, that gag is finished). Given the slight backlash over too much Jeffrey Jones in #2, it would be hilarious if Delia made the plaster head look like Charlie Sheen "on accident," with him as the voice (maybe she toyed with the acoustics inside the plaster?). I think it would be a funny new gag for Charles's character and would work around discomfort over Jones's likeness.

I know Burton didn't want Davis and Baldwin back because they'd look different, and it would be fan service, but done correctly, they could add a little extra magic to the third film. The second film was full of magic because it got the old gang back together. That same magic won't feel novel in the third film, but getting Davis and Baldwin involved could add some new magic. Maybe they aged as ghosts because of the exorcism in the first movie? Maybe they aged as ghosts because they came back from moving on? Who knows. I think they need to return, even if it's a small part.

I think some plot involving Lydia's birth mother makes the most sense, but I struggle to think of a plot that wouldn't feel like the 90s Addams Family films. But maybe that's okay!

I think BJ3 should have Lydia and BJ working together in some capacity. I imagine Charles and Delia haunting the Winter River house, Lydia deciding to live there with Astrid, and Lydia's estranged birth mother showing up to steal Lydia's inheritance from her father and Delia's estate. I'm sure the writers can cook up something better than that, but it's the most obvious plot I can see. Maybe Lydia does marry BJ at the end after helping her for a third time, or maybe Lydia falls for a contractor working at her house, and BJ marries Lydia's birth mom and takes her to the afterlife. Something along those lines makes a lot of sense to me.

Delia and Charles were last seen at the soul train station, but we did not actually see them board the train or depart the station. Given that Delia told Lydia she'd come back to haunt her, I feel sure she will if there's a third movie, and I don't have any problem with that as long as her part is big enough; Delia can't just be swept under the rug. I honestly imagine the writers will put her and Charles back in the house (though not in the attic) where some comedy will follow as Astrid and Lydia can see them at home while their visitors cannot.

I have a suggestion for dealing with Charles in the next film. I think Delia needs to sculpt him a new head to replace his missing one because headless Charles will grow old. And because people complained that there was too much Jeffrey Jones in the sequel, I think it would be hilarious if Delia makes the sculpture look more like Charlie Sheen and goes around calling him Charlie all movie, saying she thinks he looks better than ever, etc. Bonus points if they can get Sheen to do the voice and call it an acoustic abnormality within the sculpture changing Charles's voice. I think a motionless talking sculpture head that doesn't even look like Jones would be comedy gold and solve some problems.

But back on topic: we never saw Delia and Charles depart or even board the soul train, which I feel was intentional, so it would be easy to keep them in the third film without undermining afterlife rules or creating continuity errors.

I have a few thoughts on this... The time dilation issue isn't actually an issue at all. At the end of the original movie, Beetlejuice sends Barbara to Saturn during the wedding scene to keep her from stopping the marriage, yet she returns only moments later riding a sandworm. This would suggest that time on Saturn and in the afterlife isn't necessary fixed or constant like it is on earth. But either way, if Barbara could go to Saturn and back again in the middle of the wedding in the original movie, then the new movie does not break cannon.

As far as breathing air on Saturn, I have a few mixed feelings here. For one, Astrid is already somewhat between life and death in this scene, having already said she felt "weird" after inadvertently trading her life for Jeremy's. That could explain away her need to breathe. But also, the mechanism that allows Astrid and Lydia to go to the afterlife in general is not well explained, Saturn or no Saturn. There wouldn't need to be air in the afterlife anywhere, not on Saturn, not in the waiting room. Maybe it's an out-of-body experience for Lydia and Astrid, or maybe it's another dimension where breathing isn't required.

To surmise, I don't see a reason to analyze oxygen availability in a universe where living people can be miniaturized into a model town and be frozen mid-air over a giant cake.

There are a few more details, too. Jeremy has a PlayStation 1 and an old CRT TV in his bedroom. He also has a Blink 182 sticker on his furniture from the era of his death. I imagine most of the posters in his room are of similar vintage. His parents' car in the driveway is unreasonably old, even if the father had been out of work. That being said, I actually didn't predict that he was dead jas I watched the movie.