Less time road
We have now 2 kind of roads, faster and shortest I'd prefer a third choice that shows the shortest time to reach destination regardless distance or speed limits.
Seems to be unimplementable... Drive at light speed, get there very fast ;) ... how fast do you intend to drive without speed limits... 160km/hour, 200km/hour.
Right now you have options time or distance... sometimes they will coincide, if they don't Waze can't choose for you. What do you want, the fastest or the shortest route. From your description I would say you want "fastest". However fastest will always take into account speed limits as else Waze doesn't know how fast you intend to drive.