Thank you so much for relaying what he sent you!
No problem. After my PM showed that he had seen my question to him, and I didn't receive a response for a while, I told him he was full of crap. That prompted him to defend himself with this long response of various plot points. I don't see how anyone that is a serious writer could have written something that contained that many spelling and typographical errors. I also don't see why anyone from Hollywood would reach out to an unknown writer in the UK for feedback.
Frankly, this post from Reddit, which predates most of the behind the scenes photos that emerged on the internet, seems more probable:
The Ghostbusters have gone nationwide, and they've successfully become a government sanctioned public service (like in the video game), so they've branched off to different cities. Think of the Ghostbusters as Orkin pest control, and Winston is the CEO. Egon has been presumed dead for a few years because of a botched experiment. Ray has been ousted as he was involved with the experiment that killed their brightest mind, and the shareholders were pissed about it. Venkman has his own talk show (but still a member of the board).
Meanwhile, McKenna Grace, Finn Wolfhard, and Carrie Coon's characters move to a piece of property that was owned by Egon after Coon's character's divorce. It is revealed that they are Egon's daughter and grandchildren. They poke around the property and find a rusted out Ecto-1, some old, rusted proton packs and ghost traps. The PKE meter still works. The teacher at the local Middle School (Paul Rudd) is a science geek and McKenna Grace brings the PKE meter in for show and tell. The device goes haywire when she fires it up. Nobody really believes that there is a problem. After all the device is really old. Grace believes something troubling is afoot.
Janine, who is now the VP of Ghostbusters, brings a binder full of troubling reports from all the franchises across the country to Winston attention. The containment units are reaching maximum capacity, and the band-aid of building bigger ones is becoming too costly, and requiring too much power to maintain. They have to reconcile with Ray to help them. Ray recalls this problem being of concern back when the Ghostbusters first started out and briefly addressed just before their battle with Gozer. He tells Janine that Egon was on the verge of solving this problem before the accident and his disappearance.
Ray visits Egon's countryside property to see if he can find Egon's notes. Grace and Wolfhard tell him about the PKE meter. They go through the old tech,etc. and find the notes. Egon was working on opening a portal to the ghost dimension. This was Egon's solution to emptying out the containment units (as seen in the RGB series) and having a more permanent solution to disposing of ghosts. Rudd catches wind of Ray being in town and makes a visit to the Spengler home. They work together to discover that Egon had mostly figured out how to open up a portal by utilizing the technology from the temple on the Shandor building from GB1. Since the original temple was blown up, Egon had to do some research taking him to a sleepy town in Oklahoma where Shandor's followers used to mine for materials to construct the original temple. Egon was successful in constructing his own portal, but managed to get pulled into it. This portal was not fully closed and has been slowly opening back up.
Later that night, weird stuff starts happening around the farm. Ray, not having any gear with him, runs out to the barn and starts tinkering with an old proton pack. He eventually gets it fired up, only to realize that the paranormal activity is Egon's ghost haunting the place, trying to issue them a warning that something big is coming their way and gives Ray, Grace and Wolfhard some cryptic message about how to complete his work.
Weird things start to happen across the town. The Ecto-1 and the equipment is modified so that it is easier for them to chase down smaller ghosts. This is a prelude to something bigger arriving. Ray and Winston manage to round up Venkman to assist them against the "big bad." Dana comes along for the ride because "Why should the boys have all of the fun?" Rudd, and Coons' characters join in as well. As they final battle ensues, McKenna Grace's character finally figures out what Egon was trying to tell them. She and Wolfhard's character do something to officially close the portal.