I wouldn't trust an automatic process in this. Besides, video compression and the resulting artifacat can't be caught by simple averaging or thresholding, IMO.
Instead I propose another feature. When importing video, we often need to reduce the number of frames, but in an intelligent way. At least more subtle than a simple "every 2nd/3rd frame" which we already could achieve with the current timeline tools (shortening with stretch without interpolation).
So I'd like to have a tool to click on frames to mark them. I could go through a timeline quite fast and mark interesting frames (like for rotoscoping), then in the end run a script to change every marked frame into an instance, while changing everything after that (undtil next marked frame) into exposures of this instance.
TVP 10.0.18, Mac Pro Quadcore 3 GHz, 16 GB RAM, OS 10.6.8, QT 7.6.6