Here's a new twist! Take a plumber style body (popularized by plumbers, but is great for hundreds of uses), and make it work well for a S.W.A.T. Team vehicle. Harbor Truck Bodies has built several of these units. .
The top photo is a standard Harbor 12' WorkMaster Body mounted on a cutaway chassis. The SWAT modification is a standard 12' WorkMaster mounted on a Ford Crew Cab F550. What's really interesting is how Harbor has customized the interior.
The next two shots show a gun storage area with a sliding, lockable expanded metal door using the same type of locks that are on the exterior of the body (probably a different key though. . .). I'll bet that big metal door is gliding smoothly and almost effortlessly on Teflon (R) slides. They use that on all of their Cargo Bed Enclosures and it is far better than wheels with bearings.
Next is a long shot of the interior showing special storage areas that are unique to this body and fold-down seating when they need the team inside for a short trip. I love the compartments that have been made instead of the standard long shelves. It makes it so much more useful. I think I would be asking them to do that on my standard bodies as well. Plumbers would love it at least as much as SWAT Teams.
Notice the escape hatch in the roof. The roof is specially reinforced in this particular body to accommodate and support this need. You can see much of the reinforcement in place.
This type of body should work extremely well for this application and at a most reasonable cost compared to some totally custom job. With all the service body storage on the outside and all this special storage on the inside, this truck can handle a lot and the choice of chassis gives them all the support they need to make it all work together.