Sometimes I join a group ride that is higher watts/kg than I normally ride at and would appreciate having an opportunity to do a warm up with the group rather than having to go straight into a tough effort.
I wonder if there could be a warm up power button that is available for the first minute of a group ride and if a rider chooses to use it then it would make it a bit easier for the first 5 minutes. Maybe reduce the effort needed by 25%. I am guessing that the game could make it so anyone that had activated the warm up could not get on the leaderboard while it was active. If you choose not to use it then it could just disappear off your screen after a minute.
There maybe a better way to implement the warm up, but it seems that the power up buttons are already there and could be used.