I have decided to create a solution that allows you to mass-change your security settings. This is a dedicated client, and allows for more complicated security changes than simply switching public posts to friends only. It also acts as a journal archive in the process.
I called the program LJ-Sec.
It is open source (C#), of course. It's designed for Windows systems, and requires the .NET framework (1.1).
You can download the program, and optionally the source, here.
Here are some features:
This *is* an initial release, and while I haven't had any problems with post eating etc. in tests, I recommend backing up your journal with Livejournal's backup tool before using this program.
Hopefully you enjoy the program. :)
Any suggestions for future improvements will be appreciated. I've already noted that bulk find-and-replace might be a good thing to add to this in the future...