I'm really impressed with what you've done here, clearly for more fitness data geeks than I am. And you're in the early stages, so what I say is probably on your list already. The following is reaction to "ride of mine in the mountains" link above.
For somebody like me who is relatively clueless, add some ? pop-ups for every stat in the top window to tell what it is and how it's calculated. Like "perceived effort" - what the heck is that? Sounds cool, but I have no idea.
Power analytics - that power curve versus the map really confuses me. If I try to follow along, the first 50% of the chart is some tiny zoomed in section already partway through the ride, and the farther along I go, it zooms out in both directions until finally the whole ride is highlighted. It's like you're plotting average power from some random point that keeps bouncing down until we arrive at the average power for the whole ride. No idea what I'm looking at.
Power zone distribution - I have no idea what endurance, tempo, etc are. More ? pop-ups or something.
Distribution plots - these charts are awesome. But I can't figure out, on an out and back route, how I can possibly be climbing 47.6% and descending 21.8%. If it's time-based, OK, I get it. But that's not clear to me. It says "ride gradient distribution" after all. The bar chart grouping should be by distance, not time. Then I would "get it".
Ride gearing distribution - this is awesome. But how? I had no idea this was a thing. Electronic shifting tracks what gear you're in?
Analytic Charts says Telemetry Charts after you click on it. Picky, but this is what I used to do for a living.
On the pressure-based versus topo map elevation thing, you might have to get creative by country/region. How does ridewithgps do it, when mapping a route as opposed to uploading a ride? Do they pay for it? Is there a single service, or do they also "get creative"? I worked on a team implementing a "geospatial warehouse" for the USDA (United States Department of Agriculture) about 15 years ago, they were digitizing all the topographical maps in conjunction with USGS (United States Geological Service), and all that data was exposed via free APIs, because the taxpayers paid for it. I was on the backend database side of things so I didn't have much exposure or knowledge on the API side, so I don't know how you'd get at it. But it seems like somebody like ridewithgps wouldn't be paying a whole lot for it or even getting it for free somehow. It just seems lazy to upload your barometric pressure altitude when the GPS gizmo knows exactly where you are. Pet peeve.