The biggest usability challenge for me is that each crypto tool uses its own key store. kgpg, ssh, yubikey, openvpn, etc. Do you foresee allowing your client to pick up the private key from a smartcard like a yubikey? My goal is to centralize all the certs in a place that I will always have access to - and not have a different passphrase for each cert (which I will forget) or 1 passphrase for all certs (even worse). 1 passphrase for my cert-store (the yubikey) but which contains all my certs.