While I have little knowledge in modding, I know about compatibility issues and file formats. You may know some of this stuff, but this is a basic list of things.
- .bin is a format similar to .iso files. It is an image file format. It can be hard to access directly. You would need to extract the data from the bin file and convert it into a format you can mod. Even the audio of Bully is all in .bin files.
- That issue you have with notepad++ seeing the "NUL" or any other character inside of black boxes it's an easy way to spot that the app you're using is not able to read the data, which also means it can't properly save the modifications you make.
By editing and saving a file which appears that way, you can corrupt it and the game then can't read it, which would be why nothing is appearing.
- Modifications you make will also not take effect unless you first recompile what you modded:
img file --> bin file --> data --> modded data --> bin file --> img file.
- ALL of the files inside of any img file must have the EXACT same name as when you extracted it, including capital/lower letters and numbers. Custom file names are not found by the game. You might be able to do that in lua but it would be difficult.
- If any modding fails and you didn't backup the original files, you will need to reinstall the entire game again. This is a good habit to have in modding and beyond. Even the best plans have a chance to fail. Having backups will save you time and pain.
What I don't know is the raw format of the data in the bin files, so even being able to extract, edit, and repack a bin file doesn't guarantee it to work.
Hex editing tools and nifskope were the main tools in the early days. There's very little tools for bin other than imaging software. You may have a better chance in using a hex editor or a tool to extract image files unless there's a tool I'm not aware of.
