One of my absolute favourite features of Guild Wars has always been the observer feature. Allowing you to look in on the top Guild v Guild and Heroes' Ascent matches (and hero battles, when it still existed :(), it was a great way to pick up tips for those just starting PvP, and, of course, it was a great way to wile away the many lonely hours of a student trying to avoid that final essay ("I can't finish my dissertation now, the Monthly GvG final is on!")
We haven't really had any word of what format the feature might take, if it even makes it into the new game (word seems a bit blurry on the subject - they want it in there, but it might not be in at release). Eric Flannum, in an interview with GW2Guru a while back, said:
Eric Flannum: It’s definitely a goal of ours to make PvP in Guild Wars 2 as spectator friendly as possible. We haven’t worked out all the details yet but you should see something comparable to observer mode at some point in Guild Wars 2.
"Some point" suggests not straight away, but I think we can probably speculate that it will make its way in eventually (after all, without the ability to spectate I can't imagine the game would be very "spectator friendly").
The main big improvement would be the ability to rewind, pause, fast forward etc.
The issue with this would be that either you would have to remove the "social" element of it, as it would be very irritating to have some guy pausing the game at the pivotal moment to go and take a wizz. Alternatively, you could assign some kind of "group leader" who had control over these options for the stream. Or you could have a system where when you start fiddling with the playback options the video becomes "your stream" and breaks off from the action, leaving you free to freeze-frame and slo-mo to your hearts delight, and you can choose to rejoin the "group stream" once you've stopped fannying about with the fast forward button.
Add in some extra social options, a list of fellow observers, some kind of notification system for big games, maybe even a player-by-player rating system (ie, "Fuzzy Balls fought really well today, I'll give him a thumbs up! Grognak the Grawl was a complete donkey, his team carried him the entire fight - thumbs down for him!") and we'd have a pretty solid way for me to further avoid work once I start my PhD!