I think with any you have to be sceptical with anything these days, but I think the realist in me likes the idea. Brushless motors are the bomb, no doubt that this basic concept is a good idea. Putting aside concerns on how water, heat and other factors attributing to the life of the motor(s), then i think this is great approach.
I like the idea, would like to see it developed further over the years, however, battries, extra weight, etc... Anyone know much about KERS? Kynetic Energy Recovery Systems? (Formula One). This is already finding its way into the market.
Cheers POLO