#3 would be useful as long as the image quality is retained. I've always found startmovie recording far too tedious, so I'm happy there's someone with some ideas to make it faster.

More options tend to be better so you can cover people's personal preferences, but if you include options that are slower (e.g. PNG output), you should note how they will impact rendering speed/quality.

You could just record the same clip twice, one with viewmodels on and one with them off, and cut from the clip with viewmodels on to the one with them off at the moment that the view transitions from normal to "scoped in". (and simply do the same thing in reverse when they scope out again). That way you can create the illusion of continuity even though they are two separate clips.