Statistics show that in the large majority of cases of accidents between cycles and motor vehicles, the driver of the motor vehicle is at fault. Requiring a license for cycles will do just about nothing to fix this. Just yesterday I was nearly run over by a car turning left into the oncoming cycle lane and by another one who thought that the pedestrians traffic light applies to bicycles. My knowledge that I was correct in both cases did not help the least bit.
So maybe yearly retraining for drivers of motor vehicles would be a better move.