I am not sure if that is already implemented or hard to, but I’d love to have a feature a bit similar to Power Profile (the chart in the “Activity Power” tab - which is a curve displaying the best average power for a given time) … but with Pace instead of Power and Distance instead of Duration.
For instance, for interval sessions, with short recovery, I’d be interested to see what is for instance the fastest 5k time from inside that activity.
You can add an activity to the Compare-page. There you can switch your charts from time based to distance based in the options.
Or … maybe there is a Pace chart available under “Activity charts”, which is fulfilling your requirements (It’s possible to create a distance based chart with scripts).