What we did:
All of the Santa Cruz Bicycles demo vans haul trailers so they can being along plenty of demo bikes. This is the latest example we have built for them. While super simple, it does require proper layout to make things work.
We installed all mum cabinets up high to carry spare parts up and out of the way of loading and unloading bikes. We built spare tire (the bike kind) holders as well as a spare tire for the trailer, because who wants to unload 25 bikes to get at the spare late at night on the side of a highway? (At least that is when I seem to get flats!)