Torque converter clutch relies on a ground signal from the PCM at pin "T" on the case connector.

Logically, it would make sense that if you pulled the "T" wire from the connector, you would get the desired result (no TCC lock). You may need to ground that wire (from the PCM) to make the PCM happy, so it's not an open circuit. I don't know.

You may also be able to wire in a switch to ground on that "T" pin to make it manually controlled ON/OFF vs the computer control and PWM.

This is all just thinking out loud. Experiment at your own risk!