I may be behind the "8" ball on this one, but I saw a very interesting and functional pit cart design at the AMSOIL USAC National Series race.....
The teams, when running at Salem where the big rigs are not allowed in the infield,have to unload their pit equipment and then drive the haulers outside the track.
What they do is build the tool box and storage for parts into a motorized kart like a Rhino or similiar and drive that to their pit space. It's a great idea, especially for teams who will practice on one spot on pit road and then have to move to a new spot based on qualifying times.
The unit is wide though and it might be a problem loading them into the trailer versus a normal pit cart that is much narrower. I'm sure someone could come up with a narrow version of this. At any rate, it's a cool idea.