Quest-mode games
Create a custom format where people get to select quests (unknown to the other users) before the game starts (based on their available colors or archtypes). Completing a quest gives you points and the person with the most quest points at the end of the game wins. These games would not count for the 'normal' leaderboards.
See the EDH League as an example: https://drive.google.com/drive/folders/0B_gYz_k66upbRTBVal9QLUNvc2c?resourcekey=0-BzFkOFiltGkzQFkDIje_qw