I think there's a way Universal can have their cake and eat it to with Fantastic Worlds. Here's a rushed concept that I made for the layout, it is not to scale:
View attachment 9311
So as others have mentioned, it makes sense to have the lands that are parallel to each other to just have pathways between the two, but I still think there's a way to have the lands "closed off" and still be convenient to access: build pedestrian bridges above the hub.
This way, guests can travel between lands on the opposite side of the hub without having to go back out and re-scan their tickets. You could even have the entrances to the bridges be enclosed, removing sightlines into the land.
As far as the expansion plots behind the hotel go, you can build pathways to them through the hotel by building the first floor above the hub. Hotel guests just have to walk/take an elevator door down and exit via a one-way set of doors. You could also expand the hub further down through the hotel, and have it surround the nighttime show, with new "portals" being built around that section.
I don't think it's a perfect plan, but as far as allowing the hub to be an open-access retail space while still allowing easy access between lands, this is the best thing I could think of.