I had a thought, I don't know whether this is already a thing, but ... XPUBs...

If an identity was an XPUB, and messages can be written by a sub key that is hot, then you can use the XPUB to link different public keys to a single person and use each one for different things.

Eg. Key 2 can be used to receive bitcoin, while key 3 is used to sign software etc.

1 public identity, many keys that can be managed differently for different purposes.