Yes, the 2-blade w/ gyro will have pros and cons and 3-blade rotors have their own pros and cons. God knows which could be the best. Its just that the desire to remove the 2P vibration from a 2-blade rotor, which has some amount of rigidity, has bugged me for years.
Mart,
gyros will need to be actuated out of phase or forces cancel.
Correct me if this is wrong but I think that having 2 gyros counter-rotating about the same axis, but having their own independent gimbals should work.
The rotating members would be linked by 3 tie-rods, with spherical bearings at both ends of each rod. This way the two gyro disks always tip in the same direction, by the same amount.
Because they are counter-rotating, the opposing gyroscopic moments should be canceling each other in the tie-rods and not in their common axle (mast).
Hopefully, this will will result in a gyro-assemblage with only a resistance to a tipping of it's plane. It is this resistance that provides the foundation of the moment when the two blades are not providing it.
If you find that this is flawed, please say so.
Dave