This has been suggested many times in the past, IIRC.
How I have come to view the situation; These members who were here before the merit system and before the forum was 'as popular' are partly the reason there's a forum for newer members to register later on.
I had not heard a thing of Bitcoin in 2010 through to 2016, but yet users kept discussions going on here, donations, moderating, reporting many of such tasks which came with no reward.
Airdropped merits is sort of proof of the effort put in before a certain time and scrapping it out is an extreme action, imo.
This was my stand on the idea of demotion or deranking with emphasis on members that ranked up before the merit system was introduced and it still is today.
A demerit option is extreme and would definitely be abused affecting members all around the board.