MaxX was pretty much correct when he explained how the skin loading works in the OLTeamGames.u code. First it checks against a "database" to see if I have a specific skin available for that skin (All standard + ECE + CBP2 skins are included with CTF4) and then it checks to see if the *_3 skin exists in the skin's package. If it doesn't exist, then it just falls back to Jakob.
First of all, I would like to say thanks for your interest in CTF4!
Second, I wanted to let you all know that I am adding a new client side option in the next version of CTF4 that will allow you to use 3rd party skins even if they do not have green and gold versions. If a player with a custom skin is on a green or gold team, it will use the "non-team" version of that skin. I wouldn't use it myself, but it seems a lot of people would rather have a colorless custom skin than Jakob.
Now, for the solution to your problems:
There is no way to "extend" that "database" to include more skins via an .ini. I thought about doing this, but at the time I thought it would make it very easy to make your own skin cheats. But now that I think about it, I think I was wrong.
However, what if I did this in the next version:
First it checks the database.
Then it checks for *_3
Then it checks for SkinPackageName_Extras.*_3
Does that make sense? After checking to see if the green and gold skins are in the package, it will check for a
different package that is named something like SkinPackageName_Extras for the green and gold skins.
Would that be good for you guys? Then it would be easy to have a main package with your skins, and then an "addon" package that adds green and gold.
If you'd rather have something else, suggest it. Now's the time, as I'm working on the patch.