This is actually an extremely common kind of enterprise security product --- though none of them do the Javascript/PGP dance.
Enterprise security teams know, of course, that email is insecure, and that partners and clients want to send sensitive stuff via email. So they buy these products and stand them up, and then instruct their partners to follow a link to upload their documents or sensitive emails, rather than using their email client.
The box itself forwards the email to user inside the enterprise.
I think there's something useful here, but, like 'Tepix said: a simple form on an HTTPS site is already doing 99.999% of the useful work here (that's all the expensive enterprise products do, too).
A direction you can take this to be even more useful is to strip and sanitize attachments, as a way of quarantining malicious email.