You can only make 'buyer aware' with blanket information regarding the aging of this kind of part. If a buyer is buying without educating himself first that is not the mods problem: providing the part is original Rolex of course.
Just put a small warning regarding paying extra for all original aged parts in VRM and add this thread to the classic's section - then you've done your bit - the buyer (or anyone for that matter) can always ask for a forum opinion on anything in here anyway.
If someone wants to pay extra for a faded part then that is up to them. A fool and his money will always be easily parted definitely so no point in trying to regulate it - redrawing the line will only be the start of a slippery downward slope so leave it where it is.
always just my IMHO of course