it will be relatively easy to replace the body panels on this truck

IDK, if they're injection molded plastic then it kinda seems like the only way to get major damage repaired is to buy a replacement from Slate Auto. You can't just visit the junkyard and start cutting material to weld on for patches.

Slate Auto will have a monopoly in addition to having a more expensive manufacturing process. Going with plastic panels means they need less capital to build the factory, but it also means the panels will take longer to produce. Stamping sheet metal can be done fast and cheap, but the machines to do that have a higher up front cost.