If you want to have a "cart" like pit setup, I would do some research on wheels, and wheel setups. You need to have the right wheels for the amount it will carry(a lot) and it should not be able to easily drift(don't do 4 casters). One tip I would give is make sure you have breaks. So if someone worked on the workbench, it wouldn't move away into the next pit.
Also, with any electrical work you do, make sure it is safe enough to pass safety in the pits and is weather proof.(you never know when a thunderstorm is coming) As for maneuverability, I would look into a pull cart kind of system. And if you plan on buying this cart and modifying it, most of the above is redundant.