Bold part is the important part, because if the studio producing the film can’t figure out how to market it (or doesn’t want to figure out how to market it), it won’t be built.
“Halloween Horror Nights,” as an event (scary event in a Universal Studios theme park) is known and profitable in Orlando, Hollywood, Tokyo, Singapore, and (now) Beijing. The event is ubiquitous enough now to justify a standalone location in Las Vegas and will likely occur in Europe. The Caretaker, a generic spooky mortician, is known in Orlando only. Even Jack, the most marketable “face” of the event, has only appeared at non-Florida events once or twice each.
You compared Saw (which came out in 2005 and started the torture-porn trend) and Longlegs (which had Nicholas Cage) to how an icon movie could be marketed. Saw started a new trend of horror genre. Longlegs is/was the “one” R-Rated horror, not based in a franchise, to break $100m (again, Nic Cage). The next highest ranking, non-franchise horror? Night Swim at $32m. An icon-based movie is more likely going to be received like Abigail, which came in at a disappointing $25m domestic. THAT’S why they want to leverage the actual event and not a random character from the event.
More so, the people making the movie would be Hollywood-centric. The film likely wouldn’t be filmed in Orlando, and its creatives (even more likely) have no connection to the stories Orlando creates. Even a pitch for an event-centric movie is easier.
I’m not trying to insult your intelligence on this. If you had the access to even make the pitch, you obviously understand these things. But it’s the nature of the business. The best way to approach it is finding the best possible story within the framework of what the studio will best want.