Frostr does not require any nostr protocol changes, it can integrate with NIP-07 and NIP-46. What we need to do is finish our reference signing clients (so other signers can understand and implement it themselves) and then after that create a spec for Bifrost the underlying library that powers the implementation into a signing client (if someone wants to reimplement to create their own library) But none of this changes or requires anything new of the nostr specs

How are you going to encrypt and decrypt messages, mute lists, drafts, application data, etc? A big chunk of Nostr requires encryption.