Let premium members vote on future Strava features and improvements
Here is an idea that should give premium member some decision power on what areas of improvements Strava should focus on. Think about it as a sort of crowdfunding where premium members vote with their money. It should motivate some existing non-premium members to upgrade to premium membership and premium members to keep it. So hopefully this will be win-win for both Strava and premium members.
Give each premium member a fixed number of votes when they sign up for premium membership and then one vote each month. Each vote would be used towards one of a few features selected from the pool of highly requested features or improvements. Each premium member can put all of the votes into a single feature or improvement or distribute votes among multiple features or improvements. Once a feature is implemented all votes return to the member and may be used towards another feature.
This assumes that Strava would create a feature tracking mechanism visible to premium members that should be a bit more transparent than the existing "suggest an idea" forum mechanism and provide a bit more accountability on Strava side with regular updates on the improvement status. Strava should promise to prioritize development resources to the few top most voted entries.