I would like to observe that the phrase "would be" occurs with every suggestion.
In my experience, including grossly overloaded mounts that were returned to Astimex Scientific for repolishing, there were two safe and effective procedures. If there was an error on the mount's surface, then the preference was to use sticky tape followed by a quick retouch with 0.2u Al2O3 by hand. We used the common translucent variety of office tape. The tape was applied with firm finger pressure and then immediately peeled off.
If the mount had been grossly overloaded with C, then it was repolished mechanically with 0.2u Al2O3. Reworking a mount also went back to mechanical polishing. Any lab that prepares their own mounts has all the equipment and procedures required for removing C. Although I am guessing, removing Au would similarly have to be done by repeating the final polishing step with 0.2u Al2O3.
On many occasions a vendor of the plasma systems tried to sell the idea of removing C coatings. Our gut response was to ask what would happen to the epoxy. No answer and so the experiment was never done. This vendor did make one trial of providing a 1-nm Os coating. That coating was not durable in shipping. It was also visible as a higher-Z background in the SEM, although it could not be detected by XRF. The SEM is also how I would judge the removal of Au.