I’m excited about a new change in bitcoin-qt v20.0 (unreleased) allowing for the propagation of zero fee (0 sat/b) TXNs. Previously this was nerfed by the
minRelayTxFee requirement. This would allow the receiver to set the fees (indirectly) by simply chaining a CPFP TXN to the end of it. Might work something like this.
You place a bet at a BTC betting site.
If you win, the payout is a raw TXN hex string.
You broadcast the raw TXN along with a second “child” that pays the fee.
Betting site is now no longer paying fees on winning bets.
Could offer a lot of solutions to exchanges that require a “withdraw fee” claiming that they need to pay the miners. This would allow users to request a zero-fee raw-hex withdraw transaction allowing the user to pay the fees themselves.
For the more technical user this would offer up a lot of neat possiblities.