You can pretty much start in article 240 and everything you read will say conductors have to be protected at their ampacity.
If you are just using this panel as a junction box with no over current protection, all conductors down stream will have to be sized to the last over current device serving that feeder.
I think I would leave skid marks in the driveway getting away from this job unless they are willing to do it right and provide proper power to this load.
