First off, you've done some great work here. I'm really glad to see someone else is working on hacking Hardball 5. I've tried to make some sense of it in the past, but I didn't have enough knowledge back then, so my attempts always fizzled out shortly after.
However, earlier this year, I finally managed to start figuring some things out. The filename scrambling, team logo data (as well as import/export support, plus being able to use colors not found in the logo editor), player and team exports... Most everything was looking up! Then I started looking into the MSH files and ran into multiple stumbling blocks.
I guess what I'm trying to say is that I have questions, but I don't even know what to begin to ask!
This brings me to my other point.
It's funny you should say that, because 4 months from the original post date, I had finally released a "proof of concept" of a Hardball 5 tool (similar to work I've done for AKI Corporation's wrestling games on the N64). Parts of it need to be restructured, though. It was originally meant to work with player and team exports, and league data + support for other files was kind of "bolted in".
Current tool progress & source code can be found here: https://github.com/freem/HB5Tool