I think you've missed my point. If no deal is a possible outcome it's right to do some analysis and planning for it. But just because something is listed as possible under a 'worst case 'scenario doesn't mean it will happen. To assess the No Deal option fully you should look at best case and worst case, assigning probabilities, and the actual outcome will probably lie somewhere in the middle.
It seems less important now though than the issue of having to apply for an extension. And if no-one can come up with a deal that is acceptable (and no-one has in 3 years) then we either have to extend indefinitely (or keep negotiating for years if necessary), withdraw article 50 and stay, or leave with no deal