sarboy:
I was involved in the certification of an FNPT 2 in several countries in Europe. This particular machine was a single computer that drove flight model and visuals for both out-the-window and cockpit instruments. It made little sense to require an annual revalidation once it was determined that the only source of possible changes was the inputs from the flight controls.
At least one European certification agency agreed - they said they'd come and check it after one year, and if there were no changes, and if we could show that a calibration of the flight controls would be part of the annual maintenance, that they'd give a pass on subsequent re-certifications. Pretty forward looking - and no names of the certification agency!