the thing is, we would all end up using the coldest temps and softest tires for the best possible grip. i have no trouble keeping the tires in the green with R4 tires and road tires. with R2 and R1, i can keep them green for a few laps (8 or so depending on track length) then they start heating up too much.
if i am consistant, they get cooler again (due to having less grip and me being forced to slow down)
+1 for the idea, but in practice, it would be better if the temperature were chosen at random and we had to adjust the tires in the settings menu