Well if you want skyrim success then you MUST have co-op single player. I felt one of the main issues with Doom 3 was the lack of co-op single player. There was a mod that allowed 8 people on a LAN to do single play co-op and it was [censored]** amazing! More optional features = more value to users = longevity for the game. I'm sure the team has already consider different game modes for the co-op and multiplayer but standard TDM and DM should not be the only options for multiplier. I'm sure you guys have the graphics and sound covered to the max just like when Doom 3 came out, so i wont even go there.
If you need any alpha testing or feedback before launch let me know. I've beta tested many games and will give an extensive report of non bias constructive criticism both positive and negative. I also make levels on the side for counter strike source and have a keen eye for perfection.