My 2c worth. Have you considered providing PSU design details online, allowing us to fabricate our own? This will avoid the necessity to achieve certification. I guess it doesn't help you with your support model because you will never know if the builder used good components or built it right, but it would be a potential cost saver to an experience technician.
One other thing I have considered in the past is using a sense wire, but unless you design the hell out of the supply you run the risk of the supply trying to fill the bucket on a short circuit. You'd need to put some real smarts into fault detection, or have a hard- set current limit.