Neutral with all: alternative idea
For balance I've used "event = object_destruction, -0.005000" with "empathy_rate = li_n_grp, -0.2" etc etc so you have to kill about 100 nomads to get 1 square better rep with other factions. I've also re-set the Xenos rep in my game back to where it used to be.
This avoids changing the balance of the game and is more realistic, because after all Nomads are the enemy of Sirius so everyone should hate them. It's also more of a challenge to get neutral to all by killing loads of nomads instead of level 1 Xenos starfliers around Ouray.
Just my idea though. I'm not saying its the best thing to do, just what I consider the most realistic without changing the original game balance too much.