Sorry, NHRA rules require the cutoff switch be in the positive cable, not negative. It would seem to work the same, if the wreck caused no body damage, but if it did and the negative cable was grounded before the switch by being cut the circuit would still be live and the switch would have no effect
I wanted to run it through the ground, too. It would have been easier, but you have to consider all possibilities or there is no point to doing it at all.