You make a very good point!!
We have this internally and we call it “Fitness Score”. It’s a combo of your FTP + PLs + Weight.
Then you get an arbitrary number that you can see go up/down. It has very fine grain sensitivity and can be used as a metric to know your performance is improving and you’re getting faster!
IE for me, I had a high Fitness Score of 1,226. And before Cape Epic I was around 1,149, or about 6% off of peak fitness.
We need outside PLs first, but I think this could be a pretty cool way to show small fitness increases and motivate people to stay consistent.