[Nakamoto] Revisiting first-class support for mining pools

[jcnelson]

The recent service disruption on 15/16 November 2023 was caused by a fee spike. For a few hours, Bitcoin fees got to be so high that Stacks miners had a hard time getting their block-commits included in the Bitcoin blockchain on time. This lead to a chain stall. While Nakamoto would not stall in this case (the current miner just keeps mining), it would diminish PoX payouts to Stackers, which undermines the security of the system.

To address this, I'd like to revisit a proposal I had from earlier this year, whereby miners would collectively control a single p2tr UTXO that issued block-commits. The key idea in this proposal is that it's more cost-effective to mine this way than through individual block-commits, because the transaction fee for the poll-controlled block-commit is amortized across all pool participants. Thanks to the pay-to-alt-recipient coinbase feature in Stacks 2.1, the miners who pooled this way could ensure that the block reward was distributed to participants in a pro-rata fashion by paying the STX to a smart contract which tracked which miners contributed how much BTC to the p2tr UTXO.

I think we could support something like this as a first-class mining mode in Nakamoto. Moreover, I suspect this could be done without a breaking change. There is already some work on this, which perhaps could be pushed over the finish line at around the time Nakamoto is ready to go.