Route by best value rather than fastest route
Waze has, on multiple occasions, suggested long detours that are expected to only be a few minutes faster. When you consider the fuel-costs, cost to operate, etc. this is equivalent to paying a toll to save a few minutes.
If a wazer could specify the value of their time and the cost of operating their vehicle then the route planning could find the route with the lowest cost (cost being value of one minute X duration of drive plus operating cost X length of drive).
Since many wazers might not understand how to determine the correct value for their time and their vehicle's operating cost. It might be best to add a tool to Live Map to make it easy for a wazer to test various settings to get the routing behavior that they want.