For this franchise and BTTF, I would love to see an animated flick like the CGI Turtles movie. The videogame was magnificant. I don't think anyone would mind a live action movie with the same graphics, and the original voices, like the game.
I agree with Mic though. Venkman's absence could be done in an entertaining and meaningful way.
The idea a friend and I tossed around as a "fun imagining" was the following:
GB3: Hell gets so full that it begins overflowing, and as a result, an interdementional tear occurs in the center of Manhattan . After taking readings of the tear, Egon discovers that he can use the information to make a machine that can create a portal leading to the ethereal plane. This way, they no longer need to contain ghosts, but instead send them to the other side.
During a struggle, Venkman get's sucked into the portal. A little while later, he comes back as a ghost, says his goodbyes, and the GBs trap him and send him across after a sad farewell. At the end of the movie, when the GBs figure out how to close the rift, Venkman gets spit out and is alive, as it was not his time yet.
