I could see this being a use case for a NixOS deployment where your company manages the configuration file and versioning of the system, as well as providing support. Over time, I’d you’re diligent about building documentation based off of each support request, you’ll end up with a personalized guide. And if your customer decides take a break or quit entirely, they have a configured system that doesn’t lock them in into something too esoteric.
Disclaimer: I only know of Nix, never used it because I just don’t manage that many machines to be worth my while to learn it.