ON Strava if you do a grand fond etc, you can buy their jersey. I would certainly pay a small amount in order to have an electronic version of the Jersey within ZWIFT, assuming that is where the milage was done?
They do have 100km and100mile jerseys that you unlock in-game. They’re not the Strava jerseys, but same idea.
I do like your suggestion, though. Only problem is that Strava doesn’t currently differentiate between simulated and real riding.
Strava does take it to account even if it’s simulated. If you ride 100k in the game you will get the strava reward.