Look... I know it's easy to forget sometimes... but these parks are living, breathing things. That need to facilitate 20,000+ Team Memembers, millions of dollars and millions of infrasture for HVAC, Electrical, and Mechanical systems.
Those "empty" roof tops and buildings? They have plumbing, electrical, and other systems you can't see. They have tie-off points, and fall protection systems because that's how painters and techs access theme elements and systems in Diagon Alley. Those access gates? That's how they get the heavy equipment into the park to complete PMs and projects. Access roads aren't just for specific venues. USF is a loop. You need to go back that way to access certain parts of the park.
Especially something like DA, which is brand new in terms of UO, has very little wasted space designed into it. No matter what an aerial may tell you.
So no. Universal won't spend millions to frustrate guests and employees... For something that makes no thematic sense.