Agreed. I used Mailpile for a while, a lot of interesting ideas there. As for PGP Thunderbird could use one nice idea that the browser extension Mailvelope use

Agreed. I used Mailpile for a while, a lot of interesting ideas there. As for PGP Thunderbird could use one nice idea that the browser extension Mailvelope uses: have bundled OpenPGP implementation in JavaScript (OpenPGP.js) for most users (guarantees easy setup) and a bridge to call GnuPG for experts.