If Zwift separates out the Tag from the last name field, Like “ZSR” etc. Then you could sort by your ride group or race tag. The community has developed the hack to add a tag to the end of your last name, but this should really be a different field. It might be cool to also be able to make riders on the course visable/ invisable by tag. This might seem like this would be getting away from the social aspect of the game, but I can see how this would be cool for races or group rides. I like seeing everyone, but this would be a good option for others on a selective basis. At minimum, be able to sort the list in app to better keep track of a group ride. As it is now it is hard for ride leaders to see where everyone is on the course without a lot of scrolling.
So the only riders you would see on the course are those you are actually riding with. Brilliant! Methinks it might be difficult programming though. Not only are you simply removing them visually, but you also need to remove them from the physics engine, lest there be “invisible draft.”
Sounds like a great idea for races and even for training mode.