Think it though all the way.
How is he going to turn the pump on and off? With the disconnect switch? is it rated for that (not all are)?
If he wants to use only the fuses to protect the motor from overloads (bad idea), then what happens if one fuse blows? The motor will single phase and he will smoke it unless he is standing right there and notices that it is making funny noises (if it does) so that he can throw the switch. So he is essentially saying that his time to stand there watching his pump run is not worth the added cost of a motor starter.
Do him a favor, talk him in to buying a proper Pump Panel.