One of the unlucky ones who never requested a key back in 2013, but I was wondering what actually difference does having the key make - are there game files that aren't downloaded (enabling multiplayer campaign) unless the key is added via the Steam Workshop (Empire: Total War - Multiplayer Beta (App 10605) · SteamDB)?
Does anyone with the multiplayer campaign have a better knowledge of this, and whether it would be possible to force enabling this aspect of the game via modding?
Never mind, figured out how to do it.
I've asked Flinn whether posting the instructions on enabling the multiplayer campaign violates TWC's TOS or not, depending on the answer I'll update this post. Feel free to PM me else.