I generally agree with what you say, just a few things (and I promise that even though some of them look like leading questions, they are genuine things that I'm thinking about):
- if you saw the use of split screen to show the product forward hold, what did you think about that? Would you have preferred that as PiP?
- some related questions: do you think that you might want different things from an observer than a less experienced player would? Since you understand what the whole team is likely to be doing, do you think that makes you want to watch individual players more? I've heard several times that tf2 is confusing to spectate, do you think that spectating/casting single players more in stalemates would make it more or less so?
- how do you think we should balance PiP and main camera for players behind? I've found that often when I spectate the player behind things like uber exchanges happen offscreen - do you think it's worth it?
1) In this situation, I feel like split screen would be beneficial, but it would still be quite annoying to watch. Personally, I think a really smooth bird's eye person view as a team is setting up that forward hold would look a lot better. The moment the teams are able to exchange damage, then switch to 1st person (probably the attacking soldier or scout)
2) I think my suggestions apply to all observers, so yeah for example let's say it's a stalemate froyo vs ascent on snakewater (this applies to every single team; however, if you have experience you might know who is going to go for plays more than other players). froyo has control of mid on even ubers. It's possible that other players can make a play than blaze or with blaze (there are more thing to do than just suicide blaze), but for this particular map/point, you should probably just keep your eyes on blaze, seeing how he sets up before he actually bombs, not just switching to him the moment he's in the air. say it's same map, even ubers again, but froyo has control of our 2nd and trying to get last. you're going to want to keep your eyes on arekk and/or blaze since it's likely they'll both suicide. knowing whether or not they'll suicide 1 or 2 on last generally depends on the map, the score, how much time is left, the particular position of the teams, etc. but generally on last points, you'll see 2 people suicide. on other points, you'll USUALLY see only 1 (really depends, so it just comes down to experience, knowing what to expect).
3) is PiP the small screen in the bottom left corner? unfortunately i feel like this just comes down to experience, knowing when the action will happen first. however, when a player is behind and teams exchange ubers, you're going to see some interesting stuff from the player behind, so you should probably put him on the full screen and the same team's pocket on the small screen in the corner. so again, if he's too far away to really do any damage, you should leave the player on the small screen in the corner, but then switch to somebody involved in that uber exchange / resulting team fight. if the player (or any player) is backcapping, you should switch to his cam.