I've been trying to find this out since it went on sale on steam but I haven't been getting any good answers from friends and friends of friends etc.

Right now I have confirmation that Rome 2 and Shogun 2 has it. I heard Empire was going to get it. Did it ever or did they abandon it?

also just offtopic from the topic question itself, is it worth getting napoleon if one gets Empire? and which is better of the two.

Napoleon and Empire are very similar, Napoleon just covers a much more interesting period in history.

As i recall Napoleon is basically empire with more cannons and a more focused campaign. I thought napoleon was pretty good at the time but i'm not sure what the general consensus is on that.

Did either of them get campaign coop in the end?

Napoleon, Shogun 2 and Rome 2 have co-up campaigns, I have only played co-up in Shogun an that worked most of the time. imo are Shogun the better game more polished game and focused campaign.

Not exactly what you are looking for but the older games Rome and medieval 2 had a hotseat mode via the consol command.

Empire Total War has a beta co-op campaign that they promised would be in the final game, and then was promised to be patched in and never was. It's glitchy. Napoleon's online campaign is a mess, its more like two players vs. each other, and every battle is either autoresolved or the players fighting each other. Rome 2 and Shogun 2 improved this by having the players fight the CPU instead, and offered an actual co-op experience, but the games desynchronize so often that it isn't that good of an experience either.

Shogun 2 Fall of the Samurai is the only game I've been able to play a campaign without gamebreaking issues. Napoleon's multiplayer campaign (it's versus, not coop) is broke as all hell. Shogun 2's campaign is broke as all hell. Rome 2 is just a bad game so whatever.

tl;dr: Fall of the Samurai is what you want.