at the moment MB has 3 sets of folders:
1. folder for the program files
2. folder for temporary files
3. folder for the music library cache and subscriptions (the music files themselves can be anywhere though)
if you enable file associations, it also will write some entries into the windows registry, but MB doesnt depend on the registry for any operations
for 3, you can already locate your library in the same folder as your MusicBee program - just hold the shift key down when you start MB and it will allow you to create the library anywhere.
So i guess for the portable installation, I just need to locate the temporary files folder to the same folder as the program files. I dont want to have to distribute 2 versions of the program as that increases the overhead for me, so i need to think about how to do that