Seeking feedback on a proposal that will allow a transaction signer to explicitly specify what is to be serialized for the signature hash. The basic idea is to make the nHashType general enough that we won't need a new sighash flag every time a new use case comes up.
If implemented into bitcoin (via a soft fork), this would make malleability almost a non-issue (the TXID referenced by inputs just need to be updated previous TX changes) and would enable hardware wallets to securely sign without needing to download/process each transaction it spends from.
Please let me know your thoughts.