From what I can tell, Hunter is not a cryptographer, so I take this proposal with a very large grain of salt. It seems though, because he is not a cryptographer, the proposal does not choose 1 signature scheme, but rather gives users the option to choose from many. I think that's a bad idea as expecting users to understand the tradeoffs between different cryptosystems is fundamentally untenable. From a cursory reading, if one of those cryptosystems were broken, user funds could be significantly at risk. This proposal to me seems to be written by someone who strongly cares about quantum security, but is not a cryptographer so went with the classic "we do all these different cryptography things so it must be secure!"

There is some discussion about this in this mailing list thread;https://groups.google.com/g/bitcoindev/c/oQKezDOc4us/m/pIL6rZbtAQAJ including response from a cryptographer and seasoned bitcoin soft fork proposers.

From what I can tell, Hunter is not a cryptographer, so I take this proposal with a very large grain of salt. It seems though, because he is not a cryptographer, the proposal does not choose 1 signature scheme, but rather gives users the option to choose from many. I think that's a bad idea as expecting users to understand the tradeoffs between different cryptosystems is fundamentally untenable. From a cursory reading, if one of those cryptosystems were broken, user funds could be significantly at risk. This proposal to me seems to be written by someone who strongly cares about quantum security, but is not a cryptographer so went with the classic "we do all these different cryptography things so it must be secure!"