Dr. North provides something sorely lacking, a pragmatic and detailed roadmap of how Brexit could be made to work. His proposals are flawed, however, because like all British governments since the 70s, and probably much of the British establishment, he keeps on seeing the EU as a mere trade agreement that has grown too big for its britches.
Pro tip: there is reason why it was renamed from European Economic Community to European Union. Continental Europeans see it as a political project, originally to make internecine wars like WWI and WWII inconceivable, but now mainly to unify Europe under a loose federal banner to keep it relevant on the world stage. They do not share Dr. North's curious infatuation with UNECE (inventors of EDIFACT, surely one of the most baroque set of data formats ever).
Dr. North's vision of European countries rebelling against an overbearing EU to switch instead to a panglossian utopia of frictionless free trade brokered by benevolent (and competent!) UN committees is simply risible. The EU is what it is because that's how most of its member countries want it, yes, even Greece. His vision is certainly possible, unlike most Brexiter predictions, just like it is possible that Bill Gates will wake up tomorrow with a burning desire to give me a billion dollars, but it is just as unprobable.