A rotor sytem with an odd number of blades and missing one of its blades would shake itself to bits well before flight rpm.
With an even number of blades (eg 4), if you remove 2 opposing blades you would need twice the angle of attack on the remaining blades to produce the same amount of lift. Assuming you could raise the lever high enough would the resulting pitch angle cause the blades to stall?
Any deciples of Prowty out there care to enlighten us?