Where one might go with your idea is to propose an alternative second input to be used in the case where a TL input is discarded because the TL has not moved and Thrust Lock is active on that engine. Perhaps an input for brake pedal deflection could be used in place of the TL input.
Enter my vote for that one. If you have one engine in reverse and the other in thrust lock below CLB and the T/L not in Toga/Flex and you are applying manual brakes then the sytem logic should connect the dots and give full stopping authority by activating ground spoilers.