There are many considerations to take into play here. First of all, parking garages usually require level ground, so they're going to have to rip up the terrain there anyway. (Anyone who hasn't been back there, it's a pretty nice slope.) Second of all, it requires enough space to stage all of the gradbash buses during those events. That staging currently consumes ALL of the team member lot as it stands now. The likeliness of them trying to move backstage facilities there is a logistical improbability. It doesn't help the park because show buildings currently box in the park perimeter. There isn't enough space to justify building new streets on the otherside of Mummy and etc. The only ground for expansion is really the MIB plot and that is nowhere near the current parking lot. They really shouldn't move a pyro bunker into a parking garage, should they?
My thoughts are that Creative is on board to assist with watching sightlines (as much as possible) and potentially aesthetic work on the backstage areas.