My understanding from the FAA rules is that V1 is either the maximum speed at which the RTO manoeuvre can be initiated, or the minimum speed at which a take off can safely be continued in the event of an engine failure. As we are talking about the stop
case here this means that at V1 we should be (in the 737) 1. Disconnecting the auto-throttle 2. Retarding the thrust levers 3. Deploying the speed brakes and 4. Deploy Max reverse thrust. As we carry out the second action the auto brakes kick in. So max braking will not be already applied at V1.