First floor

Second floor

Now, a few notes on how this all might work. First off, certain stores would probably need to be consolidated into one so as to make the map more playable. The loft the main characters from the movie live in should also be included as a third floor, placed according to where mallofthedead.net estimates its location, and should be its own "continent". The gun store should also be included, since it isn't part of the real mall's floor plan.
The department stores should all include escalators that lead to the second floor. Each department store would be divided into two separate regions, upper and lower, which could attack each other. The central aisle that runs through the middle on both floors would be divided into different neutral regions, symmetrical among floors, and would be the main path into the various stores. Of course, some stores would be connected to each other, and some would be inaccessible from the main aisle. To give you an idea, here's a mock-up I made of the first floor. This isn't even meant to be a rough draft, just a hypothetical proposal of what the map might look like.

The gray lines in the main aisleway demarcate different regions in this hypothetical setup. Murphy's is shown as a Department store here, and would take up an area of the same size on the second floor, removing many small stores.
Also, I've already consolidated several stores here, but I know even more would have to be consolidated to make the map fit size/playability guidelines (especially with two other floors added to the map). The brown/gray areas are meant to be escalators. Each area with an escalator would attack an area on the floor directly above it, and vice versa, in addition to the areas they attack on the same floor. All aisle regions would be neutral, offering no continent bonus.
There would only be one stairway to the third floor, where the characters of the film stay, from the second floor (That "continent" would sort of be this map's Oceania).
As for the stores that would be kept, I'd say it should be prioritized by how much they appear in the film. So if it's a choice between a location that's never shown and one that's shown only somewhat, like say the candy store vs some random bookstore, the candy store would be kept, and etc.
I'd love to make this a working map, but I've never done this before, and if there's interest, I would love help with making this idea work.