1. Make a minimod on the vault
2. Make a video of ingame actual play (not test) 3-5 minute long that is nice to watch and showcast this mod
3. Post a new thread on "general discussion" forum with said video
4. Keep making some buzz on that forum with new videos/replays of the mod. Try hosting games with the mod activated. The objective is to garner support and interest for the mod in the community.
5. Make all this just before the release of a patch for faf, so that this change could be added shortly to it before people loose interest and move on.
Another solution is to try to convince the mods (Icedreamer, Sheeo etc...) so they put it directly in a patch to be tested by the community, but that hasn't worked it seems... .
That is all that comes to mind, other than that I have no idea.
Good luck, your change could really add not only to faction diversity but also to the originality, the fluff and pleasantness of the game, without breaking balance. A game is not only a shitload of stats and numbers, it needs also to spark wonder and surprise the players.