I use average watts all the time to guage the averall intensity of a session. I also compare average watts against avg hr to check fitness. The only way to do this at the moment is by continually stopping. It would be great if you put these metrics on screen or in app. At the moment the app just duplicates on screen metrics, surely adding to these could be easily done?
For now use an ANT+ bike computer to do this, but it should be in Zwift for sure!
Yes!
please get with Peaks Training on this (you already have some workouts from them) and let’s get TSS, IF, NP, etc. all in the game 
Also, who does power based workouts without looking at lap power!?