Mart,
If a heli rotor stalls you fall from the sky like a stone - there is NO mode of recovery.
Not so fast.
You recover from a stall in an airplane by lowering the pitch of the wings.
You recover from a stall in a helicopter by lowering the pitch of the blades.
Remember, the blades are 'Absolutely' rigid. They will not 'fold up'.
The only way to avoid this would be designing a "pushable" collective for -ve pitch to force rotation (like windmilling a prop).
A possibility. Another possibility would be to install a rotor-governor and not let the rotors stall.
identifying the problem before attempting to design the solution.
I looked at Nick's book 'No Free Lunch'. It says that all four configurations (Side-by-side, Interleaving, Intermeshing and Coaxial) have their pros and cons vis vie each other. It suggested getting a piece of paper and drawing four columns, then ........
Dave