I’d love to get feedback from the covenant / vault experts out there. Is this covenant scheme useful? How does it compare to existing covenant proposals like the CHECKTEMPLATEVERIFY BIP-119?
Kanzure’s 2019 mailing list post describes vaults that do not require, but would benefit from, SIGHASH_NOINPUT. The Revault team describes describes a similar scheme. To investigate the use of covenants with APO I built a vault system loosly based on the Kanzure/Revault vaults, but using the current APO branch from AJ Towns to implement them with covenants.
You can read more about covenants in the paper, Bitcoin Covenants: Three Ways to Control the Future.