I was really hoping that Apple would implement a "stress" or "body battery" type feature like Garmin and Whoop have. Adding more health metrics is cool, but taking those metrics and telling me what they mean is much more informative.
As we know the watch OS already calculates the HRV and respiratory rate for us so it would be great if they added a "stress" and/or "recovery" feature. The watch already records Heart Rate, Heart Rate Variability, Respiratory rate and Resting Heart Rate, which are commonly used in these metrics.
Understand that there are third party apps that try to do similar however I think this is an area that Apple is lacking in compared to other smart watches.