Thanks for this very good comment. You’re right. You could adjust the ratio differently to C1,...,Cn, to make sure that all EA contributors to the matching fund have reason to expect more than one dollar in total going to their top charity for every dollar they contribute to the matching fund. E.g., the fund would match donations to charities that non-EAs find less attractive 3:1, whereas charities that non-EAs find attractive could be funded 1:3.
I should have been clearer in my comment about this.
Regarding illusory matching, my hope is that the idea in the OP could solve the problem of illusory matching.
Thanks for this very good comment. You’re right. You could adjust the ratio differently to C1,...,Cn, to make sure that all EA contributors to the matching fund have reason to expect more than one dollar in total going to their top charity for every dollar they contribute to the matching fund. E.g., the fund would match donations to charities that non-EAs find less attractive 3:1, whereas charities that non-EAs find attractive could be funded 1:3.
I should have been clearer in my comment about this.
Regarding illusory matching, my hope is that the idea in the OP could solve the problem of illusory matching.