To be fair, I didn't watch the clip. But I did read something said on the thread about the player holding his breath during easy shots, causing him to miss. I'll just use my 8 years of exercise physiology education to make sense of what I'm reading to make an educated guess as to whether it's crazy or pure genius.
Holding your breath is for added strength and is called the Valsalva Maneuver. Wearing this mask is only restricting his ability to breath, and won't change his ability to use the Valsalva. A person who uses Valsalva is trying to exert maximum effort in a short period of time or burst of energy. It adds more stability in the upper body and adds power. The Valsalva can be dangerous for anyone with a heart condition and is generally accepted as a maneuver you shouldn't use. The extra effort this player is trying to add (I'm assuming he's trying to kill the "easy" balls, hence the Valsalva) will play with his timing and cause him to miss. The general cause for missing a shot is poor technique/timing (Assuming you've read the spin/speed of the ball properly). Exerting more force would certainly change the technique or timing. So it sounds like he needs more practice using maximum effort so he can adjust his timing or technique. An old exercise science professor of mine once said, "You really shouldn't try to control breathing when training. Your body will do that instinctively." Also, there appears to be no clinical evidence as to the effectiveness of masks, so I'll reserve judgement on whether or not the mask could increase VO2 max. VO2 max is the amount of oxygen your body can pull from blood to utilize in exercise. Exercise is currently the only proven way to increase VO2 max. However, according to David Blain (famous street magician) he trained to hold his breath for 15 minutes (I don't know exactly how long he actually made it). I think he may even hold the world record for holding one's breath. Each morning/evening he said he would hold his breath without exercise. Over time, his VO2 drastically improved and his resting heart rate fell to Olympic marathon levels (35ish beats per minute). Based on that information, I would think the mask could have some effectiveness in regards to VO2 max.
As for the ankle weights: ankle weights could actually cause injury due to an excessive load capacity on smaller muscles in the legs. There are lateral leg movements in table tennis that some smaller leg muscles/tendons/ligaments aren't built to handle an additional 2 lbs of weight. That kind of stress around the ankles could cause serious strain on some smaller muscles/tendons/ligaments (sartorious muscle for example in regards to lateral rotation of the hip). The player should probably focus on strengthening the legs via resistance training in the weight room to prevent possible injury via the ankle weights.
Crazy or Genius?: Not necessarily crazy, but not a game changer.
