I really like the idea and am building a similar thing with Bip39 instead of libsodium. I dont know why us software people always start with identity as the intital entry point into a new paradigm.
I agree with your implementation and because am building a similar thing, see issues with getting people to use it the same way no one uses pgp.
I suggest take a look at flow, or dapper auth and tell me what you think. Why not start with a usecase, any usecase to get real folks to play with this?
Down to working together and/or using stamp instead of bip39 in my own project