Adding the attribute-based support wouldn't be too hard. I suppose we'd still want to keep the ability for a mechanism to specify its own GUID and key derivation function, because we don't know what MS are doing for PKU2U (it's almost certainly not what one might propose in the IETF). So it could be either/or.
Don't forget there is code for NegoEx in PADL's github.
Adding the attribute-based support wouldn't be too hard. I suppose we'd still want to keep the ability for a mechanism to specify its own GUID and key derivation function, because we don't know what MS are doing for PKU2U (it's almost certainly not what one might propose in the IETF). So it could be either/or.
Don't forget there is code for NegoEx in PADL's github.