I would think that a lot of the vibration loss could be harnessed by use of what are essentially inverted speakers
overall: the real problem with all of this (none of this is strictly speaking a "new" idea) has always been WEIGHT. Can energy be captured without adding so much mass that more energy is required to delta-v the mass of the equipment than can be captured by that equipment?
"WEIGHT"
All of these technologies have enjoyed a revolution in weight saving components. I think it's time to revisit the concepts, with synergy being the hope.