Then people will start to mass farm accounts only to drive the requeriments for higher ranks lower. You supposing people will be honest and don't try to manipulate the system, what might not be true
Not sure where you get the idea from that this will be so easy. I've seen a few accounts that very obviously are linked to a posting bot. Those posts seem to be reported (and deleted) rather quickly usually.
And if the automated approach should work, then what prevents them from using it to "farm" for high rank accounts directly (in a fixed requirement rank system).
All that said, the deviation defined rank idea looks very nice to me and has a certain nerdy appeal, but in reality, it's not really worth the effort probably. Introducing a new rank each 2 years with about twice the activity requirement is a hack, but an acceptable one imo.
The current activity required for "level up" are 30, 60, 120, 240, 480, ~900 (middle of 775 and 1030).
So, maybe we will need a new rank 2 years later but then it will be 5 years and 10 years, as the activity required for the new level will be doubled every time.
