You will have alienated a major economy on your doorstep
Yeah, and it will definitly hurt us. But I fail to see how, logically, the UK will be hurt comparatively less. You're not just gonna WTO trade with us, but also with the rest of the world. How will it be bad for us, but not for you?
Existing deals with countries outside the EU are already being what's called 'grandfathered', i.e arrangements rolled over as far as possible. It'll also be very easy for the UK to trade access to its markets for agricultural products in return for services (etc), which is something the EU struggles to do due to French objections.
It will hurt the UK, but the damage will mostly be sector specific. In the medium to long term EU exports to the UK (your largest market) will become increasingly uncompetitive assuming the UK goes down the path of trade liberalisation. The flip-side of that is prices in the UK, both for consumer goods and inputs for industry, will on average decrease. You'll also see onshoring as UK firms pull back operations from EU27 to Britain. UK tech industry, the biggest in Europe, will also benefit from escaping particularly burdensome EU regulation (for some reason Brussels has a death wish when it comes to digital technology).
You also have to recognise that the UK economy is c.80% services. It's easy to continue servicing EU customers in the event of a 'no deal' because all you need is to open a 'brass plate company' and employ a handful of people there, or some kind of 'eResidency' scheme. By contrast these options aren't available to German heavy industry.
