Hey! Honestly thought you had moved on as nothing was receiving replies.
I can't get into specifics well (posting from phone and will likely be 8-12 hrs before I can fire up my computer again), but basically your mod was redefining everything for the character and then overwriting vs changing only those specific things that needed changing for the character animations and pictures.
Some mods, when by themselves, yes do work with yours, but only because they put in extra logic if yours is loaded. This causes problems when yours and theirs are not the only mods loaded. Ex: try loading realistic flashlight, minimaxime, and this mod together. The GG character will have the realistic flashlight, while the default won't (or was it the other way around? Again, posting from memory on phone). And if you add other character skin mods into this mix, they'll be similarly affected (default flashlight).
I believe Pi-C tried getting a hold of you a few times about this.
If you want, feel free to rip my code in its entirety to update yours, but yours has also been like this for so long that many mods have special case handling if yours is present that will still break things with other mods (like realistic flashlight).