Your distinction between NOS and mint makes a great deal of sense, but I'm unclear why, in your definition of mint, the history of the watch and its parts should play as significant a role as it does. If mint is based solely on appearance, then it's unclear why a replaced part, provided that it's replaced with a correct part, should alter the description.

To be mint would require that a watch owner know, and be capable of proving, the watch's history. I don't know if that's possible, unless the owner is the original owner. Other than that, we rely on the information provided by the previous seller, which may not be accurate or, more significantly, provable. We may know what we see, but we can't guarantee that a 40 year old watch hasn't had a well done repair over its lifetime.

It seems to me more important that it have the appearance of a watch in perfect condition than every part be provably the original.

Also, since I come to Heuers from the classic car route, we expect some restoration to be done over time to maintain a mint appearance. Time alone has an impact on appearance. A mint car is expected to have had work done to maintain that level of concours appearance, and it's not considered a negative. The question is whether the restoration was done properly rather than whether it was done at all. If one can't tell that restoration has been done, and the appearance is no different than it would be the day it walked out of the shop, then it seems it's as mint as it could be.

Just my two cents.