Just remember that the CA certs (that anchor ssl trust) is usually also distributed in a similar way (on the install media). The difference is that you can more easily independently review the trust of any given pgp key (you've personally verified the key, or have personally verified the key(s) of someone that have personally verified the key).

I suppose in theory one could take a snapshot of CA keys, sign them with pgp and use that a s "know set" (note: not known good, as there is no way to be able to fully trust all the certs typically supplied as CA roots -- a subset could probably be verified). But that's not how the CA system is designed.