Thanks for the idea, Cem! I've changed this post from a "Question" to an "Idea." This is somewhat similar to how we currently calculate drive scores. Half of the points are dedicated to speeding while the other half are dedicated to hard accelerations and brakes. We are, however, planning to refine how we calculate drive scores, so stay tuned!
We've considered tracking idle time, but as of now, we're not planning to factor it into scoring.
Hi Cem, While we're not currently planning an eco-rating like you describe, we are working to improve the scope and accuracy of the drive score. We may end up creating something that addresses your idea, but in a different way. :)