"Charlie don't Surf!" , Boy was Kilgore right
In this game Charlie does nothing cause Charlie doesn't exist, and if you don't know who Charlie is, I mean the Partisan, yes, the Partisan.
Since no one talks about them I assume everyone is glad they are gone, but I miss them. I seems strange that know, when Civ finally gives you a real unifed nation to play (and not a bunch of city-states unified under your administrative control) they take away the ability to wage wars on national liberation.
Partisans should be useful, especially at threatening units in the rear, like workers, and cutting lines of supply, as they did in WW2. The unit should be 4/5/1, and appear after nationalism, though it could not be built in your cities. You woulg get Partisans in 3 ways: When a city falls, a number of Partisans equal to the number of citizens resisting in the city is created within the old cultural boundaries of the city, in difficult terrain (forests, jungles, mountains). They then can be used as regular units. Every turn more partisans are created equal to the number of resisting citizens- that would be the method of recapturing your city, not the seemingly random mathematical formula used to figure if the city returns to its owner or not, in the process detroying units fortified there.
The second way is that if the enemy razes the city, a number of Partisans equal to half the number of workers created, (rounded up, so one worker, .5 partisans or 1) also are created, trying to take revenge for your murderous ways.
Finally, and most importantly, you should be able to go into cities you just lost(and so should the A.I.) and for a sum (usually hefty), recruit partisans from your enslaved population to fight, perhaps even turn one of your ensalved workers into a partisan (who would kill enemy workers or liberate those of your nationality). The partisan from cities would be created randomly on the city radius. You could not do this any more after: 1.peace is signed between you and them, 2.the city converts to their nationality.
Finally, you should get a grace period of some type after your last city falls but workers or partisans are alive (when your last city is taken, you get partisans), of about 3 game turns, in which time your allies could liberate one of your cities, and then you could get it back in diplomacy- thus allowing for something like government in exile like many small EU nations in WW2.