V3 transaction policy for anti-pinning

[instagibbs]

@ajtowns

With just the v3 constraints, I think you’d want to design your protocol such that either parent transactions only have a single output that’s spendable immediately – that way any CPFP spends will naturally conflict with each other and RBF rules will apply,

If you are expected to be able to conflict the parent this isn’t necessarily required.

e.g., exchange doing a batched payout can sign multiple versions of withdrawals at different feerates and confidently replace them with up to 1kvB overhead if customers attempt sweeps. Locking customerss addresses with 1 CSV isn’t a think you can really do.