I wonder if a better solution would be to be to only allow video evidence at L2/L3 matches from match cameras, instead of some dude's cell phone. Put a GoPro or equivalent on the head of whichever RO is currently running the timer and another camera high up on a tripod so it can see as much of the stage as possible. If you're really ambitious, put cameras on the head of every RO on the stage.
Advantages:
1) Every competitor gets as close to the same video evidence as possible for their run.
2) Since the cameras would be standardized, equipment to review video evidence could be standardized too. If a call needs to be made with video, pop out the memory card and put it in the MD's known-good video-evidence review tablet. No issues with trying to view the video on some tiny cell phone screen.
Disadvantages:
1) Yet another device the match director has to provide and ensure that it's functional and charged (in addition to scoring tablets, timers and radios).
2) Some shooters will still take their own video for social media or their own personal post-match performance review, and if that video isn't allowable as evidence they'll be mad.
For L1 matches then I think cell phone video or whatever would be fine.