Not to many people played White Knight Chronicles but i do think there system for co-op was pretty damn good. It could be a way in this game to use the same idea. Except for when for when you rank up or start different jobs working for people your hut or keep would upgrade. Place for you and a group to meet up before heading out into a battle or something. If you are unsure about the system i speak of its worth a check out. I have been waiting for a game with that type of system since that game closed down, and with co-op possibly coming i think it could be amazing add to the game. Not asking for a mmorpg but a co-op system would be great dealing with a group of people on your own is impossible, and who knows what the future acts hold, hoping huge battles.
Techincally speaking Cryengine is capable of supporting multiplayer, so if a group of modders came together they could build something similar to what the guys from Skyrim Together are building, but I highly doubt any type of multiplayer/co-op will be implemented by game devs.
Hey there is always hope!