If you're talking about private keys, the distiction remains: either you want to export/import what is in an already encrypted wallet (useful for backup), or you want to do encryption separately. The intent here seems to be the second case, which is fine. It just means you'll need to both the wallet passphrase and the key password ready if you want to import.
Absolutely! The goal is to handle the keying independently and not depend on the master key of a specific encrypted wallet. So, if it were used for exporting, it wouldn't be as convenient as "backupwallet," and at least one export password would be required. But it could be implemented to be more convenient than dumpwallet + GPG.
Also, considering the used version byte, could you follow
this thread? I'd say encrypted privkeys form a new data class.
Thanks! I posted a note to the list and referenced that thread.