The thing is that it doesn't have to be a full-blow mode. Just make it so people can switch between all the perspectives and you're practically done. Even just something like that would be a tremendous help for people who want to stream tournaments and LANs. And it would also be great for all the people watching the streams of these events.
If their "bandwidth issues" are because they're using resources for something like a live action film instead of working on their actual game, color me a super sad panda.
I'd actually argue that a spectator mode would help sell a game more two or three years into the future than a live action promo would on initial release.