I enjoy riding against my own segment times and trying to beat my PB.
I was thinking Zwift could incorporate a fitness signature to firstly measure progress but secondly easily identify those around me who are of a similar ability or organise group rides based on a fitness measure rather than watts/kg.
This is based on an INDIVIDUAL effort on the Watopia (or maybe other worlds) segments. So no drafting (TT Bike?). When you complete a segment in this way at an all out individual effort your time is recorded and this is what makes up your Zwift Fitness Signature.
Segments could be but not limited to:
Epic KOM
Volcano KOM
Hilly Reverse
Hilly KOM
Hilly Fwd Lap
Volcano Circuit Lap
Sprint Fwd
Sprint Reverse
The times of the above would be presented in a radar diagram to display your profile and highlight your strengths and weaknesses as a Zwift rider and perhaps where you would like to focus your training. When ordered on the radar diagram by segment profile you will see if you are a climber, sprinter, all rounder etc.
This could also be used to match riders ability in group rides/races.
To do this you could convert times into fitness levels. So for example if you take the slowest segment time for each segment and call this level 1. For every 10 second gain from this time would be the next level so 14:00m could be level 1, 14:10 could be level 2 and so on. (may need to de different for prints)
You could even go as far as displaying a riders level live in game depending on what segment they are on but if it makes up a riders profile this could be used as a fitness/training gauge that can be applied to group rides/races etc.