I'm new, but would just like to put some input (btw great job on the mod, I love it and I could care less about the minor issues that I have read in this post).
On the subject of partisan unit as a resistance unit. I think that it really can't be a infantry, but more like a spy in that most resistance wasn't military battalions forming up and taking on the enemy in straight up battles, but more in the lines of harassing infrastructure and guerrilla attacks could have specific mission like destroy infrastructure (in a certain amount of turns, start revolt in a city and weaken unit like 1 or 2 strength).
Also a feature like a government in exile could be a cool idea and triggered if X% of original cities are lost and that the capital has been captured. Could work like a Mongolian camp (from I believe the warlord scenario) spawning a unit every once in a while (only infantry and maybe light tanks). The Gov.-in-exile unit would go to the nearest alive ally's capital. Would give a reason for the French to evacuate at Dunkirk to fight another day instead of fighting to the last man in the last French city.
Also add a new civic for exiled govs so that they can have a lot of free units so don't go broke.
Of course this would probably way to hard to implement in anyway, but its just my 2 cents.