I owned a TNA and I didn't know until reading this thread what co-op mode was. It sounds like a good idea to me, although I personally never would've played it even if I cared to figure out what it was (I saw the splash for it in attract mode). I can definitely understand the appeal and I think it'd be nice to see in more games.
In the team play mode do the players on the same team also share progress? Based on what I read in this thread I'm guessing they do, but just want to make sure. When I saw the splash for that I figured that it would just be team scoring like in Segas/Sterns.