Tex-Hex would be a nice addition. I wonder what made them leave him out of FGB in the first place. Maybe because he didn't seem the type to be a minion of Prime Evil. However, he fits wonderfully in BraveStarr too, of course!
I had a huge, huge brainwave last night regarding Jake and Eddie's first actual bust as Ghostbusters.
It should take place at a Renaissance Fair, so that we can introduce Long John Scarechrome, whose ghost ship is causing havoc at a Tall Ships regatta, and reintroduce Trance-a-Lot and Frightmare, who interrupt a jousting match and put the spectators to sleep! Come to think of it, Mysteria, Apparitia, and Fib-Face could be a part of the festivities, too, given Fib-Face's penchant for disguises and Mysteria's overall "Morgan le Fay"-esque appearance.
Now, this RF should take place within San Francisco, because I want the boys to drive to it at first, only to get caught in a traffic jam, but that's when they discover the Flight Mode on the Ghostmobile. Also, it's important to reintroduce Sir Trance-a-Lot, because this triggers the memory of their fathers busting him at Castle MacDougal all those years ago.
When they radio their dads, who act as advisors (at Ghost Command or investigating in the field?), all parties are horrified to learn that the ghosts can come back from the Spirit World.
And this establishes the crux of the film: The Ghostbusters must act as detectives and figure out how the ghosts are able to come back. Is it a fault of the Dematerializer? Or is it an external influence??
Here's another great concept, one that should make this entirely different from the Columbia Pictures series.
Jake, Eddie, and Tracy (and their fathers before them) are not "the best, the beautiful, the ONLY" Ghostbusters.
They are but one of many, many teams that have existed throughout our history.
Wizards, knights, samurai, merchant-marines, cowboys...the list goes on. (They're not all part of a family-tree, mind: The genealogy only starts with Marshall Clinte back in the Old West.)
Zero chose his agents based on prior contact with the paranormal/supernatural. He gave each team a Dematerializer that was disguised as something period-appropriate (the medieval period = a wizard's scepter; the merchant sailors = a small treasure chest; the samurai period = a Ninja Turtles hand-lantern, etc.)