I recently read about
Pedro de la Gasca. I think his time in the limelight would make an excellent basis for a campaign.
Scant decades after the Spanish conquistadors take for themselves the Aztec and Incan empires, the crown attempts to halt some of the worst abuses by passing "
The New Laws". In Peru, Gonzalo Pizarro, brother of the original chief Conquistador of Peru, raised a banner of revolt and killed the governor.
The Spainish King had recently been embroiled in a number of wars throughout Europe, and had no troops to send to the new world. Instead he gave a bishop extensive Royal Authority (on paper) and sent the clergyman (La Gasca) to the new world with no money and no army. If that doesn't sound a like a job for a player character, I don't know what is.
What abuses will you tolerate, and which will you pay with in blood? how do you convince the mostly unsympathetic but rebelliousness forces in the north to supply you? How do you balance political goals with the likelihood of success?
Several different scenarios present themselves to my mind. Playing out the historical situation may have more depth and richness than others, as well as making the setting easier to flesh out. Its not for every group, but I think I'd enjoy this option.
Setting this sort of adventure after the traveller interstellar wars is also interesting. Abuses in the conquered territories by fleet admirals have been reprimanded, leading to a rebellion. The PC's are sent from Terra with a small ship and authority from the terran confederation, but very little in the way of resources. How do you deal with these rebels, especially when some of them are heroes from the last war...
Fantasy versions are also possible, if harder to construct. I just look at this sort of scenario and see lots of room for courageous action, hard moral decisions, and player empowerment.