Early days yet, but it would appear that the cost of reverse thrust, including its 'mishandling' by piolts (eg. full reverse at speeds less than 80Kts. and not stowed below 60Kts) causing expensive FOD (damage)
Ahem! My B737 FCTM has this to say about use of reverse thrust during landing: "Maintain reverse thrust as required until the airspeed approaches 60 knots. At this point start reducing the reverse thrust so that the reverse thrust levers are moving down at a rate commensurate with the deceleration rate of the airplane. The thrust levers should be positioned to reverse idle by taxi speed, then full down after the engines have decelerated to idle. Etc.
I can see nothing there that would indicate danger from FOD if the above procedures are used correctly.
With regards to heat dissipation being better at high speed on the ground and that being a factor in the perceived advantage of the autobrake system applying brakes on wheel spin up. In the short period it takes from touch down to taxi speed, the reduction (?) of heat build up due to higher airflow over the brake units at high speed would surely be of no consequence. In any case, the maximum heat attained within the brakes occurs up to 30 minutes after the aircraft has stopped. That is one reason why a brake fire warning can occur well into the climb after take off and not necessarily just as the wheels are tucked away in the wheel-well. The heat build up increases once the landing gear is retracted and cooling airflow is diminished.