I don't understand this space very well, but I wonder if an iFixit-esque solution would work there: publish DIY guides on identifying and fixing common faults, and have a network of sellers for replacement parts and tools.
Absolutely a possibility. Solar systems, especially when not connected to a grid, are fairly simple beasts at the end of the day. Simple enough that I've seen more than a few youtube videos where guys build out their own custom solar system on a van.
There's only a few parts that go bad (it's probably a capacitor somewhere).