LOVE the film viewer, use it all the time; both as a training tool and simply to capture screenshots of great shots, etc.
One thing that I really think would help in the training tool department would be a toggle that brought up an informational HUD with visual indicators of several things.
I know the image below is crude, but bear with me here haha...
So, upper left - a crude representation of the current aileron/rudder inputs... elevator would be nice too, but my Paintshop skills are limited haha...
Upper right, aircraft damage indicator.
Bottom right, alt, speed, G force.
All of these things can be determined elsewhere, but when you're trying to discern someones specific maneuver (or your own failure) - having all of this right up in your face at once would be great!