First, Creative has nothing to do with Halloween Horror Nights. The event is created by Entertainment and designed by the team known as Art and Design (A&D).
Second, the Show Director who is predominately in charge of Streets is Blake Braswell. He is the individual who oversees their development and implementation. That said, it's still produced by committee. It's not one person's ideas--it's a group of people coming up with ideas and deciding the best ones.
Now, with regards to where they put zones: They have essentially put zones all over the park at this point, except the London Waterfront. That includes the street between Transformers and Shrek (which use to be known as Shrek Alley). That street help Night Maze, War of the Dead, American Gothic, and others. I think the main reason they don't put zones there is because of guests flow. They want guests to easily navigate through the entire park and all of the zones without back-tracking.