It's impossible, because you are even on a freelancer ID always red with nomads and wild. The only way to change that would be an SRP.
What comes close to it, though, is the Zoner ID or the generic Freelancer/Miner ID. You can bribe yourself to grey or even green with any faction on those IDs.
With the exception of Cultits, Nomads and Wilds you can get on neutral rep with everyone as FL. It just takes time and a lot of missions, bribes won't work that well, just for the beginning. It really takes a lot of time and knowing how many missions you can do against whom to still have them neutral but yes.. possible.