I don't know about that failure mode, Rev, I think your still looking at a spring loaded needle, similar to the vacuum petcock but with electricity. Granted, the electric means the spring could be much stronger, but if a piece of trash lands on the needle, it's still going to leak.
What we need is a manual petcock with a small gear-head motor attached. And of course you'd need some electronic logic to operate it, but I think that would be pretty simple. The motor would only run when turning the petcock on or off, and there would be a simple manual override if it failed. And there would be an LED to go on your dash that would indicate if the petcock was not closed.
Edit: I see mention of a 'Teflon piston', so I think that valve uses fuel pressure to stay closed. If it does it might not work so well.
Whatever method you use, it's a good idea to test it periodically. Even manual petcocks have been known to leak, so pull the line off now and then to check for leakage.