Don't they already do this? Linde/Still & Jungheinrich seem intent on making it as difficult and expensive as possible to service and repair their trucks by control of their software and diagnostics. What's needed is some sort of standard like the car industry has, OBD2. You can buy a fault code reader for less than £30 on eBay. I believe some fork trucks now use OBD2 for engine diagnostics. Personally I think things will get worse before they get better, I doubt there would be agreement on a common system.