Also, to rank up from newbie to jr. member atleast some number of merits must be kept. Doesn't matter even if it is one. This will limit spammers, multiple account users and shit posters from joining the signature and bounty campaigns from the start.
This is a more realistic scenario. In my opinion, the major rank transitions that require a merit component is Newbie/Jr/Member and Full member. Once you've gotten past Full member, then the transition is less drastic, and merit is less problematic. Though, if you have made it to Sr. member under the new system, in time you'll eventually make it to Hero and beyond anyway, so there's no point changing anything.