Another issue with this proposal is that you would get lag in your anti-torque control. Direct drive tail rotors work on small model helicopters because the tail rotor has so little inertia it can change speed really quickly and you don't get any control lag. On an R22 sized helicopter, I imagine there would be a noticable lag and on a significantly larger helicopter, I can imagine it would be difficult to control.
Another issue is that with vibration and fatigue. One of the reasons that helicopters are designed with a specific main rotor and tail rotor RPM is that it makes it a lot easier to do the vibration analysis and ensure the helicopter doesn't have any nasty resonances at the operating RRPM.