It’s a very good question - I did the original scripted module reload code many years ago and it took a while to sort out all the tweaks needed to get it working, so I never went back and looked into the options multiple-file reload, which is too bad because it tends to make me put more than I should in the main scripted module file.
Probably the same techniques that work for the main module would also work for imported files and maybe there’s even a way to discover the dependencies automatically and reload them all or maybe the scripted module could provide a list of code to reload. It may also be that with the python3 transition there will be new ways to do this, I haven’t looked. Would love to see a PR for this.