An excellent thought. Generally though, 7.2V bulbs are pretty much done at
50W. Not that your point isnt valid. In application, the Vbatt will not be all that much higher than Vbulb. I can make the stipulation that the Vbatt to Vbulb ration should not exceed 2:1. The switching FET I plan on using for really high outputs is the IRF2804S. I've used it in a PWM softstarter design I built to run 600W labp at 30V.