Brain dump on "Thresher", inspired by playing with tornado.cash on ethereum (see http://gavinandresen.ninja/a-more-private-eth-wallet ). "Thresher" because it accumulates deposits until some minimum threshold is reached, then pays out.
The problem: tornado.cash deposits and withdrawals are fixed-size, with a minimum size (0.1 ETH in the case of ether). Anybody that uses tornado properly will accumulate less-than-minimum amounts of ETH in different addresses and be unable to spend them without compromising privacy.
Note: I'll be talking only about ETH for the rest of this gist, but the idea obviously applies to any of the tokens supported by tornado.cash.