How big a Ghostbuster team would work?
I was thinking that you could stick with the traditional four or maybe six, but then also have player “buddies” who aren’t busters but hang out with them or whose stories interact with theirs. A bit like Buffy’s Scoobies. This would help build the relationships around the team, which was a big part of the movies. It would also allow for a whole lot more players, and they wouldn’t need much in the way of costume.
Movies generally consist of two fairly equal parts, the action line and the relationship line. In Ghostbusters the action was the busting and investigation, but the relationships were the love interests, issues with the villains, etc. The action is what you remember, but the relationships are what make it all feel involving. Mordavia had a bit of a similar approach.
Rather than having the whole thing follow the busters, you could have action happening in multiple venues simultaineously and involving a whole cast of player types. I can think of heaps of interesting stuff that PCs from outside the team could get up to in that setting.