Looking at the voting on the Rate the Race thread for the Chinese GP, you would have to say that your safety car proposal is excellent.
Better at shaking up the race than any other method, and popular apparently.
Random number generator for the lap on which a safety car intervention will take place, and a second dip for where in the field the car will insert itself.
E.G. Lap 20 position 5.
Apparently what is wanted according to the rating of the Chinese GP.