This seems to be aimed at a single security domain like a company. That's not what you have in many cases, and supplying a public key to a remote site for login

This seems to be aimed at a single security domain like a company. That's not what you have in many cases, and supplying a public key to a remote site for login, revision control, etc. is actually tractable. There is actually longstanding experience with a "global" PKI in the research community with Globus, specifically as a hacked-up GSSAPI mechanism with ssh. It was widely detested as I saw a few years ago. (They could have used Kerberos without inventing and messily implementing all that.)