Before you waste ANY more time on this idea, you have to understand one core basic concept about what you are thinking of doing here.
100HP at 230V single phase is going to require over 420A of 230V single phase current! You cannot get around that fact, and in fact because of losses in the VFD and transformer to go from 230-460V, you will actually more likely start approaching 500A of 230V 1 phase current. Unless your customer has some sort of extremely unusual service from the utility, I seriously doubt he has anything larger than a 400A service, which in reality is actually going to be limited to 320A (because that's the limit on meters).
I have another customer in a similar circumstance that has a 1200A 230V 1Ph service