To explain, a private group system would be one in which you could make a password-locked group with only you and people who know the password, and make markets there only for people in the group, and have a leaderboard of mana earned inside that group. Maybe also a mana limiting system that the group owner could use to cap maximum amount of mana spendable on each market?

This is designed to notify manifold devs of what I believe to be a cool idea.