A kill-switch doesn't HAVE to completely short out the signal. All it has to do is provide a sharp-enough contrast between full volume and some lower level. That's why, before anyone ever installed a formal kill-switch, musicians simply used the pickup selector switch and quickly toggled between bridge and neck pickups. So, simply placing a lower value resistance between output and ground with the switch, to attenuate the signal, may get you the desired effect without the undesired side-effect.