Everything in vanilla clearly states the Nomads were actively attempting to destroy humanity from day one. They are not a peaceful race that wants to coexist and original lore states Sirius is theirs and humans are dirty disgusting trespassers that are stealing their birthright.
Nomads should return to being the big bads. Gallia is old, boring news.
Should've sent Kusari and Gallia to war, had the Nomads big bad out of nowhere and nuke Gallia, then go ahead with them having an actual crack at the rest of Sirius.