UPDATE:

Don't spend any time on my issue I posted earlier, as I've found the issue and it's now just a matter of finding the correct solution. This might end up being of interest to other people. I'm using the Super Orders mod and so far everything has worked perfectly with it, but this problem is directly related to the use of that mod. I will report back more when I find a fix. I can tell it's doable, but doing it right is going to take some time.