are alien slaves with psychic power considered viable starship pilots?
possibly they’re just not as viable as troll pilots because trolls have been bred to ideal, and troll psions are simply superior.
Thing is: would there BE alien psions? And if they were any superior or equivalent to trollian psions, I don’t think their species would be conquered easily - they’d more likely be nuked from orbit because Condesce had no qualms against eradicating one of her own species’ castes when it was too difficult to rule over, so she’d have even less issue with commiting genocide against another race, even if it would be valueable as psychic batteries.
Alternative, of course, would be to make them into a client state with privelages that usual conquered species lack, like some independence, maybe even colonizing or spacefaring technologies, and leaving them be so they’d see trolls as benevolent overlords rather than monstrous conquerors… but it doesn’t seem to fit Condesce’s personality. She’s cunning and brilliant when she wants to be, but she’s also incredibly wasteful (especially with her own ‘human’ resources), and makes stupid mistakes like trying to force humans to reproduce like trolls with no means to actually genetically modify them (even if trollian bioscience is likely advanced enough to do so). So, yeah, I can’t really see this.
But the entire idea that psions would be harder to subjugate flies in the face of how Alternian society works on a basic level; if the majority of the troll race are lowbloods, who are most likely to have psychic powers, then I see no reason why a psychic alien race couldn’t be dealt with in the same way.
Psychic trolls seem pretty vulnerable to other psychics attacks, for example; Aradia, when properly prepared, could easily beat the shit out of a highblood with her powers, but she was totally obliterated by a goldblood jacked up on mind honey. And even said goldblood’s powers, despite being exceptional, were easily countered by a sea dweller with a laser harpoon. If the alien powers were mental rather than energy-based (like Vriska’s powers as opposed to Sollux’), then highbloods could counter that with their superior mental fortitude.
And none of that is even to consider the sorts of unintentional side-effects of colonisation, like diseases that trolls are immune to but certain aliens are not.