Hey all, Bartek from l2beat here. We are in the process of finalizing the implementation of the ranking which will be released soon. We are hoping for one last final feedback - please check out l2beat forum post and consider providing your feedback
As a teaser, we are still trying to decide if we should go with a simple, linear ranking as proposed by Vitalik, or it is better having slightly more complicated (but hopefully still easy to understand) more multi-faceted maturity ranking that could look like the following mockup.
Have your say 
