I've been sitting at my desk for the last couple of minutes studying my own conducting style. I've always tried to maintain a very clear beat (a lot of my conducting over the years has involved beginner bands, so communicating where the beat is is far more important than it might be in more professional outfits.)
Anyway, I've noticed that my style is very three dimensional. My upbeat, for example, starts near my sternum, goes out from my body and follows a roughly circular path back to near my forehead. The other beats seem to do similar things. Now that I'm looking at it, that back-and-forward axis is quite pronounced, and may explain why my tuba players (who sit on my immediate right) never complain that they can't read my conducting.
Which goes to your original point---depending on the conductor, a side mounted camera might actually work, so long as it can still read two directions.
The problem I have now is that I'm going to be very, VERY conscious of my style come Thursday night!