It feels like it would be counter-productive to assign people levels. There is a sort-of two-tier membership level already: The Life You Can Save Pledge (>1%) and the Giving What We Can Pledge (>10%). I encourage cheering people on (and engaging with them in a productive conversation) no matter where they currently are - even if they are just giving $20 to an obviously non-cost-effective charity.
Here's an absolutely phenomenal tool for creating diagrams of whatever level complexity. yEd Graph Editor even has auto-layout which creates graphs with least overlap. http://www.yworks.com/en/products_yed_about.html
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