I have always felt the truck needed to be designed to fill the needs of the operation. Most all the mechanics I've known wanted bigger; a huge crane, 25 CFM plus compressor, at least a 300 amp welder, bolt bins, tool box drawers, 3 foot step bench on the back, air conditioning and all the big lights. Problem I've had in providing them and getting them set up is why do we need that truck when it will never leave a mine site or we only work on skid steers, TLBs, small dozers and maybe a telehandler. I can't see the expense for a big truck if you aren't going to do major work. Big truck means big tires, more insurance costs, higher fuel consumption, CDL license, higher maintenance and repair costs and so on.
So if I'm talking to the pencil pushers I'm lining up the types and frequency of work that needs to be done using the truck and the costs of hiring outside venders to complete what you don't have the right equipment to perform. They don't understand the wear and tear nor the risks of getting something running again when the truck crane is too light or doesn't have the reach needed to pick a swing reducer out of the excavator. Do you have another machine capable of the lift? How much production will you loose? What if you have to work on tracks in the field. Do you need the 1" drive air wrench? That should define your air supply. Do you run a wire feed welder? Maybe that will define the minimum size welder. You have to do your home work and present facts that can be acted on by the office geek. If they don't listen, then don't kill yourself making them look right.