you can do that but from my experience pouring concrete, you'd have to do a 4x4 area under each lifter foot to ensure against cracking and that's if you have the minimum grade tensile strength concrete recommended.
Yeh, I get that its a complication. Not sure How Ray's is, cause I think its a continuous slab @halifaxhops
Could do separate slab for that area. Don't think you want all one in a 30x 40 anyway. A few smaller and less likely to have cracks later. I know in the cold storage the crane runs for setting steel and roof units were thicker slabs than the rest of the floor.