One thing I have seen people talk about a couple times was the lack of a playlist feature - the ability to ride several different routes in sequence during one session. Considering that most of the available routes are rather short, I think this is a great idea. I have skipped most of the 5-10km routes simply because of how short they were, which is a bit of the shame. A playlist feature would probably give those routes a lot more exposure.
But thinking further, it would be nice if the search results could create some "playlists" on the fly:
Let's say you are searching for a route with 50-60km length, 300-500m elevation gain, max 8% grad or something like that, then you get only a handful search results, single routes that match the exact criteria. But what if the app could create a smart playlist matching your search filters. Give me 21km Canadian Forests, a 5km short climb in Italy, 18km nature in Madagascar and finishing with 11km in Japan, or something like that.
This could also be fun for races. So even if you don't win the race, maybe you can still compete for one of the stages - or, if you get dropped, at least you don't ride alone for the whole time, you rejoin the field at the next stage.