It would be nice to have the ability to calibrate a trainer without having to quit a ride. Perhaps a PAUSE function that temporarily suspends the game so you can do a trainer cal, and then jump back into the ride.
Alternatively, a warmup period could front end the game itself…although staying in sync with friends would be key. Maybe the graphics would just be a rider sitting on a trainer during warmup…that way the friends would all remain at the start of the ride after they’ve warmed up