Any backstop is anathema to the pointy heads who back him up. I cant see that happening but we plumb new depths every day. He is getting a pasting on tv at the moment.
You have to wonder, though. His recent defeat at the hands of the Supreme Court makes anything May suffered pale by comparison, and he is still trying to sell the sunny stories about the big, beautiful deals he'll be negotiating with the EU, and then with the rest of the world. A connection to reality doesn't appear to be his strongest suit, to put it mildly, for if one thing is clear by now, he isn't even seriously negotiating with the EU. That, quite obviously, isn't the way to go if crashing out "by accident" is what he intends - say, by formally demanding an extension, as required by law, while providing a justification for it so feeble and flippant as to be laughed out of the room by the EU, and then running out the clock.
With BoJo at the helm, you cannot possibly rule anything out, no matter how immature or imbecilic. The only thing I know is, he's fighting for his survival in office against the mouth-breathers from the Brexit party, and whoever thinks, "There is a limit, THIS he will not do," whatever "THIS" is, may very well end up surprised.