I love the way everybody jumps onto the engine damage bandwagon whilst totally ignoring the dangers involved with the total blockage of the pitot static system. Especially after the Air France event that could have been caused by a similar situation albeit rapid ice blockage. I admit fully that damage to the engines is extremely concerning the other dangers are no less worrying!
Whilst we train regularly with volcanic ash encounters, leading to unreliable airspeed, in the simulator having to do it for real with a full passenger load is something I would not particularly enjoy!
Pitot heat and anti icing systems won't work for an ash blockage and, as we can't see the clouds/concentrations on weather radar nor do we have any detection instrumentation apart from the unreliable airspeed sop's (which would be pretty much closing the door after the horse has bolted), I think operating commercially would be risky.
Positioning flights with paid professional aircrew ok, passengers? Maybe not.