I sometimes merit old posts with the thought in mind that eventually airdropped merit will be eliminated or the rank requirements will be increased so that airdrops wouldn't be enough. less often now that spending a few months inactive caused my source to get hobbled.

One possibility would just be listing the grandfathered rank separately.  "Hero Member / Legacy Legendary".

Of course, my perspective on the relative ease of getting merit is no doubt highly atypical.

FWIW, Satoshi has received enough merit to rank legendary.