@ Solarius Scorch
However, your idea to make it time-based made me think, and I actually like it, with one small change:
You don't have a month. You have 24 hours. (Much like with a normal terror mission.)
Can also be different depending the cities number, and some spice can be added with random time allocated (ex: random from 10 hours to 50 hours, random from 1 day to 5 days; but le time allocated is indicated to the player).
@ Hobbes
I like the idea of how the map should be designed but the objective behind the mission isn't really appealing. Players in no doubt would try the mission until the novelty lasts but afterwards my personal choice would be to rather ignore the lost country than having to play 3 missions to liberate it.
Some rewards (clearly indicated/surprise, and even randomly done) can also be added (and even special missions in city/base, see this thread:
https://openxcom.org/forum/index.php?topic=2469.0 ).
Rewards examples:* Clearly indicated:Report indicates a large stock of Alien Alloys/Elerium-115/Weapons/etc. at this city/base.
Etc.
* Surprise:10 percent of saved Civilians joins the XCom team for free (initial hire cost).
A contractor in building construction, happy to be saved, will build for free, and in half the time of construction, the next 10 facilities built in your bases.
A billionaire, after seeing a Chryssalid from close enough for him, and VERY grateful, donated $10 000 000 to the XCom project.
A genius inventor specialized in weapons, gives you all knowledge about a special technology (choose a research for free about weapon/armament, or/and new type of weapon/armament, etc.).
Etc.
So the player can choose the base/city mission he is interessed in (and also can have some surprises).
And, this can be done during the "liberate all cities" time or/and before/after.