Mart,
for hands off hover .... An absolutely rigid rotor with seriously impractical cone angle may do the trick.
I agree with all that you say, except for the use of the word
"impractical".
Hopefully, a large fixed coning angle of 4º or 5º will be practical for stability during hover and also for stability during forward flight.
During fast forward flight, an Absolutely Rigid Rotor will not provide any
flap-back to give speed stability. This is where the higher than normal coning angle should be an advantage.
This large pre-cone angle should assist with speed stability by offsetting the nose down drag, which is caused by the fuselage.
Dave