Using the Battery.bmp file?
I've ripped out the whole VGA section info.
I changed the file size to read in Hex and the file opens in Engie File Converter.
That tells me We CAN adjust things just in Hex.
Next thing to try is to cut just a single section and run some decompression tests. Then re-compress for comparative.
Given what I did so far? I could probably extend files beyond stock features.
It's understanding the file structures and how the Game uses them that is the Key!
Andreas86 provided so much information that is helping greatly! So do NOT forget that this IS a Team effort!