Even the 4-bangers suffer from an enclosed TCM, leaving the external circuitry restricted to CAN lines. Very likely to be designed that way to prevent just what you're trying to do (which wouldn't surprise me in the least).
I did write to Wholesale Automatics asking them about a TCC lockup switch for the YD25-powered Navara RE5R05A box and got no response. They have these for other models and even the Nissan Patrol with the RE4R03A box, but no response to my query so I became a little disappointed and now have doubts about their after-sales service if their pre-sales service is so lack-lustre.