So the 'expert' could only come up with "water might not be good enough to transfer the amount of heat that will be produced"? That's not much of a hurdle, really. Start with different materials: use coolant, for starters, instead of water. Also: the vehicle is being levitated by powerful <i>fans</i>.
The obstacles brought up in the article will certainly be technical challenges, but to write the entire project off as "impossible" is simply closed-minded thinking.