I am an offline dynasty guy, but I can see a lot of potential in a spectator mode, and I completely agree with you.
I have a feeling a spectator mode for NCAA would rock for a lot of people in OD's especially with the popularity of party chat.
1) Members could scout opposing players by "attending" their games.
2) People could ensure members are playing by house rules.
3) Maybe give the players or just the commissioner the ability to secretly view ongoing games to help ensure house rules.
4) It would allow everyone to view each others big bowl games, critical regular season games, or just random ongoing games for the entertainment value of watching football with friends who may be on the other side of the country.
5) It would be pretty awesome if the EA website saved replays of the games as data files like Halo does so that everyone could go back and watch any particular one of dozens of past games. (Maybe limit the feature to only the current season perhaps if need be?)
6) Watching other players games would allow new players to learn the game faster.
7) Maybe allow an optional test phase for new members in an OD where they can submit sample game films (or just have them attached to their profile) so an OD can determine if they want the player. It could also allow the new player to watch films from the new dynasty so they can see if in fact they want to join.
8) I can guarantee you it would be more fun to hear the commentating of your whole OD during the national championship yelling with you over an insane pass to win the game than hear whatever bland commentary the game offers up.
9) It would be huge if the game allowed you to watch live OD games over the internet as well. Would be a great distraction from work, school, or an airport
Such a mode could maybe allow you to send typed comments in for everyone else to see. If Xbox enabled it maybe even allow you to join in on the voice chat or at least hear it.
10) If you don't have the internet to stream #9 maybe allow an ESPN Gamecast mode where you can watch the stats pop up from the games.
The Gamecast mode should also be thrown onto the xbox if you just want updates on how the game is going while you are watching netflix or something.
I'm sorry but I just see so much potential for a spectator mode and it never even occurred to me before since I am an offline dynasty guy. Coaching Carousel would be great as well, but has been talked to death about already. I think both features together would improve dynasty mode tremendously.