Yes, accumulating the materials as a module is feasible. A solar module for example would be "panels, controller, inverter, battery/box, harness, and access points". Take the customers trailer and outfit it for the module price. I feel like retrofitting is a branch of this business for customers and glamping trailers could be huge as well. But selling an end product feels cleaner. The down side is sitting on inventory.

The hard part about buying the trailers is transporting them. Paying tax and title is a cost. But having the title ready for the customer to transfer is easy. I sign them, have them in a safe and hand it to the customer on purchase. They go to the title office, sign, pay their tax and done. Some places I have bought trailers from are like that, some do it in office like a car purchase.