Maybe one of us can make something?
For N gauge, I was thinking of a very simple system using muscle wire, using a small length of it running along from where the connector is mounted to the top if the "hook".
Here's a pic:
The wire would be looped, so a small hook n the back of the connector would be handy, and I was just thinking of superglueing the wire at the bogie end, a small dab should do it. The power sires can be run alongside the pickup wires to hide them. I guess you could even colour the muscle wire to hide it.
running the wire along the same axis as the connector allows the connector to move freely whilst in normal use, but when a current is applied it will lift the hook, hopefully decoupling. By just using muscle wire it is very small, so can be bogie mounted or chassis mounted depending on model, and would be very simple to install. Just need some muscle wire to test with