How about: make kopeks zero-sum. Kopeks represent credits and debts, not absolute wealth. You can transfer kopeks away from yourself as long as your kopek total stays above some negative limit (your credit limit) which depends (probably linearly) on the number of VCs you have. Members with a negative number of kopeks cannot leave the union. When someone leaves with positive kopeks (or leaves by force majeure with negative kopeks) you then have a bit of a problem, possibly resolved by redistribution. Or, to avoid that problem, the union tracks kopek totals even for non-members, but only members are able to transfer kopeks away from themselves.
-zefram
