Well that kinda changes a lot of things.
1) Hows your parking situation?
2) Do you have room for an outdoor queue line?
3) Just my input, utilize the main floor for the entire haunt (you'll need it!) and use the basement for actor prep, especially since you have an out of site access door there. Knock down the offices and turn that into your real maze.
4) Any way with real construction equipment you could knock down the dividing walls between the cells so you could create SOME sort of zigging pattern, cause right now it looks like a straight walkthrough....not scary and groups will see EVERYTHING happening to the group(s) infront of them.