Decided to spend the day doing some quick coding and made a img editor specifically for bully which also removes the need to rebuild archives after replacing or editing the contents.
Extract the attached rar into any dir and run it. Direct it to your .img file you wish to open and just use it how you would img-tool. I strongly suggest making a dir where your img file is and extracting it there, then modify the files you want overwriting the old ones in that dir.
Here is how I do my directories for this:
Then just create a new archive of the same name where the original one was. Please make backups of your original .img files before working with them to avoid reinstalling the game again if you make a mistake. If anyone wants I will create a full howto on modifying .img files and creating them from scratch, and post said howto's in this thread.
I fully tested this app and it works flawlessly for me and hopefully it does for you. Anyways, have fun using Bully Img Editor.
here is a screenshot of the editor:
