Which Walt are you referring to, the chap with a dream of making an HP42 ?
It would take a lot of effort, but the technology is certainly there !
It's just a matter of money; as the racing car driver ( Craig X ? ) and the chap in "Mad Max' put it, 'speed is just a matter of money, how fast do you want to go ?!"
I'd be quite happy to trundle around in a HP42, and see the scenery rather than in a Concorde.
Walt's are berks who pretend to be ex-miltary with illustrious careers; this chap at most offensive would be called an optimistic dreamer.