The only sensible way to measure income is with purchasing power, and that's far more complex than an exchange rate (since many of the services and goods originate in the UK anyways).
Giving the same deal that they have right now is what will give further fuel to leave. Why should I stay when I can have a better deal leaving?
That would provide perfect ammunition for nationalists everywhere.
See:
http://newobserveronline.com/brexit-contagion-germany-fears-...
In what world is punishing having a worst deal that they have now because they don't have the duties?
And yes, you talk about mutual beneficial union, that is not what UK wants
Do you have read your link? Because it says that the contagion will happen if there is a good deal with UK. Just the contrary you say