So we went into the locker thing more in the general thread. The more I thought about it and heard other opinions, I think it may actually be a great idea, it's just all about the execution on the ops side.
As far as exiting - Technically, you don't come directly into the Discovery Center, but after leaving the building and passing by a kiosk which looks to be for on-ride photographs, the path only leads into Discover Center as of now. It's possible they could change this, especially because it was a preview so things may be different when live, but that's what they were doing for us.