I think there's misunderstanding here
a- I understood your argument perfectly. However please understand that Switzerland/Norway has a very different deal to what the UK is suggesting. In fact, if the UK wanted a Norway's deal then I can see that being sorted quite easily. The Swiss deal would be a tad more difficult as I suspect that the EU regret that deal and want a way out it.
b- Regarding burning bridges, I was referring business wise. Even then though the EU-UK will still negotiate on WTO terms which is a vastly inferior deal to the one the UK currently enjoys with the EU. WTO terms doesn't deal with services either which is what the UK is more concerned about.
I believe that a deal on WTO terms will hurt the UK's economy significantly. However the biggest damage will be the effect on society as a whole. A no Deal Brexit will probably bring the end of the NHS, an erosion in worker's rights, the end of the manufacturing, farming and fishing industries etc. Those would have a direct impact on the very Brexiteers that voted for it. I think that the repercussions to it will be far worse then the economic impact itself as no one likes to be taken for a ride. Speaking of being over dramatic the effects will be far less then having two atomic bombs dropped on London or Liverpool or having to foot the bill of an entire WW