Having written a small part of the whole story, I know it's going to be a trilogy.
Part one: 1985: Dana's moved away and has to cope of her separation with Venkman. She meets a Milla Jovovich kinda neigbor who's attracted to her and problems ensue. Meanwhile, the Ghostbusters have to meet with the mayor to clean up the town of the pests removed by Peck and his friends. The latest is sued by the Ghostbusters for illegal procedures and looses all rights of performing environmental service ever again. Dana recalls to Ray and Egon of her problems as she tries to avoid Venkman as much as possible. Only then, her neighbor gets possessed and tries to finish the ceremony that got started in GB1.
Part two: 1986-87: Dana and her girlfriend keep on their lives in another part of New York. She finds a nice job opportunity in a museum to restore paintings. Suddenly, her love disappears. Dana calls an old friend she met in high school and enlists her to find what happened. Menawhile, the Ghostbusters have lost Winston who got a job as a security guard in a shopping center, since the GBs can't afford him anymore. Jeanine leaves soon after for a new job in the food service and not too soon after this, they're forced to close their business. Dana and her friend find out that her girlfriend is captive of the spirit of another yet unknown worshipper of Gozer and that she's about to resurrect the demon into this timeline.
Part three: 1988-89: Dana is searching for her girlfriend and her old friend as the two possessed women try to bring back Gozer in her human form and into the most available body as possible (mainly Dana's). At the museum, Dana meets a musician who seems to have interest in her. She is told that the museum will undergo some changes in administration. Janosz Poah will be the new head chief in the restoration wing. Dana finally breaks the spell and fights her friends to free their souls. It works, big time. Her old friend dies while her girlfriend is told that Dana breaks up to marry her new man. It all finishes (for now) with the birth of Oscar in january 1989.
That's how much information I can give about the storyline and as much as I know. I try to stay true to the elements of Ghostbusters without making it Austin Powers-like or some such thing. There probably won't be much comedy since it's a trilogy about Dana and her environment. The GBs are doing small parts in the story to fill in the blanks of what they are doing at this time and if Dana needs them, they are still available to her (well, two of them at least). I hope this sheds a positive light on the story I'm trying to bring.