Having watched the green bits at the end of the runway getting closer asked the crew politely why they hadn't selected reverse power.
What type of aircraft was it?
I think it's most likely that Wiz is correct and if they had followed your line of thinking the auto brake system would have simply scheduled less brake when the reverse came in in order to achieve the same deceleration rate. If they were braking manually then more brake pressure would have done the trick unless they were at max manual braking like Wiz said, if they were.....my goodness that must have been exciting!