Just saw this game as part of the "Countdown to 2013" sale and was wondering. The episodes are 50% off this week and it seems like a large amount of content for 800msp. No coop is a deal-breaker for me though.
But it would probably be that player one (host player on PC, game pad on Wii U) would be Daryl like in Single player, and then the others connecting would be random survivors. I don't see how it would work too well. The way you progress is by vehicle, and the amount of survivors you have is based around your vehicle. What happens in multiplayer? Do you take up another seat and boot a member of the team? Idk. But I think that you should start with like one random survivors and people can join as him/her, but then in single player they're just computer. But then you're still able to have them killed, kill them, boot them.
I sadly just don't see it working. Maybe it could be 2P only, and at cinematics, you both go to Daryl's point of view for Merle to talk, but otherwise P2 is Merle. I dunno, but it isn't looking good. :(