The wagon works.

I have been modifying some of my OO rolling stock by applying staples to the drop arms of the couplings. If you look closely, you can see the staple attached to the coupling on the brake van. Also the staple that has been bent to shape, to fit the coupling arm,  they are secured  with super glue.
This system seems to be working very well with the magnets I've  placed between  the railway track sleepers . Hands free uncoupling.