Stop signs and signals might be a little frivolous, since Waze already tracks expected time to get through a junction, in any direction, from any approach. And, the last thing Waze needs is another dramatic "WATCH OUT!" warning (like for every single stopped car on the side of the highway) that occurs so frequently during a typical drive that you want to throw your phone out the window.
Instead, what might actually be useful is to take this expected travel time through a particular junction to a second degree in measuring how confident Waze is that you'll be able to get through that junction in the expected amount of time or faster. Mathematically, I would imagine this to be based on a function called standard deviation. Clearly, routes largely utilizing freeways with relatively lighter traffic have the least deviation. However, on routes that utilize expressways with signals, the reliability of an expected time starts to deteriorate, depending on how you catch lights. Finally, on routes that pass a lot of stop signs or otherwise unsignaled left turns at busy junctions, the expected time breaks down completely, as there is no telling how long you may have to wait.
Wouldn't it be great if Waze could at least utilize this degree of information to present to you, along with your route options, for each route, how confident - maybe as a percentage - Waze is that you'll arrive at or before (but not after, even by a minute) your ETA?