Many thanks for your suggestion and support for TrainingPeaks Virtual.

I'm delighted to say that this is already fully implemented. Simply select the "Join Rider" option from the action bar at the bottom middle of the screen (or if you've got a keyboard, the use the J for Join hotkey). This will bring up a menu allowing you to join any of the pacer bots, or any of your friends that you follow, or anyone else who is on your team.