I don't believe that the separate ladder for teams would work in reality and here is why...
In WC3 or COH, sure you have something called AT and something called PUG or PUB, and there are separate ladders (stats) for both. However, in COH and WC3, AT manly refers to 2v2 games. So, unless anyone is suggesting there should be a separate 2v2, 3v3, 4v4, 5v5 ladders and queues - it is safe to assume that only 5v5 games are considered "team and competitive games" in DG (the same is with DOTA no?).
The point is there is not enough people to have a system where there would constantly be 5v5 games between teams of comparable skill (ladder) . Hell, the most populated place to play DOTA when I was playing it was DOTA league, and it is organised as a PUG, but with a scoring system (somthing like pantheon is now but needs more people skill data and maybe even better skill measuring algorithm...)
For arranged teams, there are custom games (some CW channel would be great) and, may I suggest, a periodic online tournament with prizes and, of course, front page coverage etc etc. Periodic tournaments would make winning it much more important then some ladder season, and would involve the rest of the community (PUBs) much more (esp. if the replay system starts working).
Bottom line, if you want a good competitive 5v5 scene, you need to have a good and populated PUB scene. Also, you need competitions that really matter, not just some "point gathering" system that would come down to what team can play more games during the season.