The Nomads got bred by the Dom for the only purpose: to protect the Dom vessels and territory at all costs. Since their purpose or being as been planted deep inside their genes, there is no way to change the reputation to the Nomad's, for anyone. Nomads will attack everyone, but Dom.
... to be added. Humans investigation about them can be read HERE.
Nomad Outpost - Styx (Best guess)
Nomads are represented in several systems within different sectors of the universe, such as Nomads Lair, Unknown systems, Hidden systems, Dyson Sphere, Outer Dyson Sphere, Freeport 7, Styx, Mandar, Gladius and Gurm.
Destroying Nomads vessels will have negative influence at the reputation with the Dom.