No, don't do this. People who use the GPG system can handle the decryption of themselves offline.
Simply encrypting the message via JS is just ~3 lines of calling a premade library on the JS side, and a new DB column like the added Bitcoin addresses.
Then they can encrypt it themselves offline too, It takes less than 2 seconds to encrypt it using that site. what's the point of semi automatic pgp system. lazyness?
People who PM me might not know what GPG is, have it installed, or know what a keyid is. They don't need to even know what it means if encryption is automated.
Now, if you
are using GPG, then it should be assumed that you have it installed and know how to decrypt.