So... How long will it take more or less? >///<
No one can tell. They need a skilled hacker to look into the files. Unfortunately I'm not qualified but here's my insight
Their img.bin is basically an archive file which consists of multiple PAK Files, which are, again another archive container format
The main archive format seems to be PACK though. From what I see, there seems to be compression involved as well.
There's a file table at the beginning which is essential for repacking.
It contains the entries and file sizes of each individual file. Now if they insert their stuff, other than updating the file sizes and offsets, everything would have to be shifted accordingly.
The NLPUNpacker could be modified to do what it already does in a way, but it's incomplete.
The basic idea is you got a BinaryReader for Reading, now you need a BinaryWriter for well um writing = repacking.
In this particular case, things are made hard by the fact that the files are compressed. The hacker would have to either make it work without compression (= bigger files) or make their repacker recompress their files again.
Sounds easy enough, right? Now they just need someone to do it. And until they do, they can't move forward.
This might take a week, or a month or a year. No one can really tell.