I think it will be great to build a New Challenge Series - Strava Grand Prix for running, cycling, swimming, and triathlons.
This is important because:
Athletes like challenges that are connected to each other and lead to bigger challenges
Strava can partner with racing organizations to build the Strava Grand Prix and earn challenge badges for each event. The Grand Prix can be a paid and unpaid series depending on if the athlete wants a medal + swag bag.
Completing the Grand Prix gets you access to a special event at the end of the year and a Strava medal + swag bag
For example, Abbott World Marathon Majors has six races for the six-star medal. Strava can create it's own series for different sports by partnering with different major marathons around the world