I see. So, if I set up an intricate browser clean-room environment, and I assume that the Javascript verification system you come up with actually works, I can get some of the benefit of simply installing GPG and using POP mail.
How do you know which public key belongs to the address? Key servers? Web-of-trust? Look it up on their homepage?
Scramble has an address -> pubkey resolution system which balances security with usability.
At least with Scramble you can create a secure USB stick to boot from with all of that preconfigured. Any solution that uses bare GPG still has severe usability problems.
I salute what you are trying to do, but you have to understand that the Js browser method, as it stands today, is a dead end.