@Hoodlum:
There's a wide gulf between "not actively attacking Phantoms" and "being able to dock on Phantom bases". The Outcasts, as a group, do not hunt the Phantoms. You could say they are "neutral" to the Phantoms. This does not mean that they have white rep with the Phantoms on their repsheets, only that when they encounter Phantom players they don't go "ZOMGPHANTOM" and open up. Well, usually.
Anyway. Phantom-Nomad relations are... weird. Any previous "decisions", like how there are Nomads in the Phantom guard system, or how at one point the Hellbound was partly "crewed" by Nomads (though that was back before RP was serious), is pretty much nonsensical. To be honest I don't think anyone has any strong feelings on how that interaction should work- and it gets even more complicated now that the Phantoms have been abandoned by the Crathgyan.
However, your Cult is unlikely to know of the alien-assisted nature of the Phantoms unless either the Phantoms or the Nomads told you. The Phantoms don't exactly go around proclaiming themselves as slaves of the Crathgyan, after all, and "faction of well-equipped psychopaths intent on destroying the Houses" can be applied to a wide range of other groups that didn't have alien backing.
As such, I'd say it's best to treat them with the normal wariness and occasional cautious cooperation unless one of them tells you about their Crathgyan benefactors.
As for the Corsairs... when I'm on my Das Wilde Scorpion drone, I don't say "Corsair". I say "murderer", "desecrator", "trespasser", "graverobber", you get the idea. They are NOT to be considered friends of the Nomads. Kill them all.