How about some ‘extreme’ jerseys awarded at certain milestones, for example when you hit 100,000 or 200,000 metres or 15,000 km or ride for 8 hours straight, or 25 times up Alpe du Zwift etc.
You get the picture. No challenge to enter, these are just based on your overall stats. For us ‘25 ers’ waiting for the next level/challenge.