Would it be hard to wrap it in a script that does that for you? I'm not familiar with GPG but I can imagine a smart hacker made it so that you could basically pipe it through.
True, not particularly difficult. At the moment though I just keep GPG encrypted text files if I handle encryption independently of jrnl then I lose a lot of the value of it like being able to search by tag.
1. Create a file foo.org.gpg
2. Put this in the first line (you can list multiple PGP keys if you like):
3. Profit!