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.
There was some discussion of including it here https://github.com/maebert/jrnl/issues/262 but it looks like they might have decided against it.