removing / disabling rear heater system?

I am planning on removing almost all of my seats and trim from the rear of my Hiace. Along with that I plan on installing a diesel heater. This will make the rear heater system redundant for my needs. I am curious as to what everyone recommends for the most graceful/simple way of either removing or disabling the rear heater system so I can put some blank paneling over that area and reclaim some cavity space for either the diesel heater or other electrical needs?

You can delete everything from the rear heater up to the valve unit that's operated by the lever in the trim panel, and then just take the rubber coolant hose that's forward of the valve unit, and close the loop at the hard lines. I had to do this due to a hard line closer to the heater matrix that was leaking, and it was quick and easy to do. Be prepared to lose/catch a little coolant in the process. It's possible you could delete even further forward, but this is probably the easiest access point.

Awesome! Thanks!

Also check my diesel heater install in the 'Modifications' section, as I did what you propose.
I don't go int huge detail, but the placement I found is close to where the old blower lived, as the floor is nicely accessible.

I’ve also installed a diesel heater in the cruising cabin version and then relocated it to be more effective.

https://youtu.be/59m-RBV0y_Y