Extremely anecdotal evidence, but I'm being reminded of Warsaw Uprising, in which, along with makeshift equipment and Allied contraband, mostly German inventory marked with Polish colours was utilized.

I do think those Rebels should spawn under special rules and have liberating the city as their absolute priority. Hell, maybe even make it something that previous owner can invest into in their occupied cities, to make them spawn quicker (maybe late tech unlock? Once again I'm thinking WW2 and all the airdrops provided for various local resistance movements).

Yeah, I'd love to see several sorts of "rebels" with different priorities in the future, including "Resistance Fighters" who can retake their occupied towns, "Independent People" who've been willingly liberated by the empire and generally play neutral, "(True) Rebels" who are created from low population and seek to "liberate" their own cities, and a few more...