And I really wish there were more career specific talents in BC (heretek has a lot of them, and some enemies have interesting abilities as well).
The bird of hermes is my name, Eating my wings to make me tame.
The Navis Primer describes a sorcerous Warp Guide on page 118. This sorcerer uses sacrifice to gain the aid of the denizens of the Warp to guide his ship through the flows and eddies of the Immaterium, and can even improve that ability to quite serious levels by doing more sacrifices to the Dark gods. Practically, this means they make a sacrifice and can then act like 1D10+10 days as Navigators, substituting their Forbidden Lore (Warp) for Navigation (Warp). To improve on their skills, every other sacrifice they make increases their tests by +5 up to +30. Of course, in RT this goes hand in hand with 1 corruption and 1 insanity, but I do not think this would bother those who have foresaken the Imperium.
Friedrich van Riebeeck, Navigator Primaris, Heart of the Void
You could always just roll a navigator from RT and drop him in BC, it's what I currently play and there isn't much difference once you convert the stats.