the likes of C3PO [...] become 'free' (partial citizens - but free will for employment) when they 'pay for themselves'...
I see it that way, as well. Once you've got a robot with intelligence, it may desire equitable pay rates, and may also develop personality quirks, hobbies, preferences, and so on. After all, they're not stupid.
Eneri:
Shalena in bagaan, X-K-Bar. You look concerned. What is it?
X-K-Bar: I was talking with the other pilots in your fleet. They get paid Cr 6,000 per month.
Eneri: Yes, that's correct, X-K-Bar.
X-K-Bar: I think it is only proper that I, too, receive a salary.
Eneri:
Niiku. See, here's the thing. I bought you from Makhidkarun, so technically I
own you as property. In fact, I'm still paying off the
kugganzir loan for your purchase. What's more, I pay for your upkeep, your monthly maintenance checks, your yearly fusion replacement cylinder, and so on.
X-K-Bar: I understand; in fact, except for the loan, I note that you cover a portion of maintenance costs for your
biological pilots, as well, as employment incentive. However, last night I downloaded the Imperial legal code for civil rights, and it is probably cheaper for you to pay me a salary and drop some of the maintenance costs, than to pay the court costs of winning a civil rights lawsuit -- and it is not necessarily a guaranteed win, I might add...
[...]
Alternately, some robots have a brain, intelligence, education, and skills, but have memories erased, and are designed to slave away. Among those, a percentage realize they are essentially 'asleep' and start to seek their lost memories. Some may be like replicants from Blade Runner.
And even if they are devoted, brainwashed workers, intelligence still demands that they have down-time to relax. Maybe some of
those become quasi-religious about their employment, in effect worshipping their Builder and proselytizing for the Builder Megacorporation:
Eneri: Hi, X-K-Bar. What can I do for you today?
X-K-Bar: Oh,
shalena in bagaan, sir!
Eneri (waiting):
Shalena binerii, X-K-Bar... so what's up?
X-K-Bar: I just wanted to say how
radiant you look this morning, sir! I don't know how you do it, but everything you do is just so
suitably you!
Eneri: Ooookaaaay. Thank you. (pause) Is there something else?
X-K-Bar: Uh? Oh! Yes! Sir, I was talking about the Corporation to some alien robots, and I think I may have a contact for you!
Eneri: X-K-Bar, you know we've talked about this. You don't have to convince other robots to align themselves with the Corporation. There are many Corporations that build robots such as yourself.
X-K-Bar: Oh, but Sir does jest so! Those are all
false corporations designed to
deceive the chosen robots of our beloved Corporation. I remain ever faithful, of course!
Eneri: Of course...
In other words, they are another type of alien NPC.