I agree with Sacrenco.
If this deal is passed, in six, twelve, eighteen months, nobody will be talking about different VAT, customs rates in NI. Certainly not the Remain parties. Certainly not the business and farming communities.
The only way it becomes a political issue once again is if DUP or Orange Order make it an issue. Considering the predicament the DUP finds itself in today this would be political suicide.
The 'cant be a border in the Irish sea' stance is the greatest hoax perpetuated on the people of Ireland and Britain for over a century or more. Nobody lives in the Irish sea, no communities potentially antagonised with border infrastructure, no businesses disrupted, no working people impeded at check points going about their daily lives.
The DUP already agreed that checks could occur away from the land border between north and south. Those checks would occur at air and sea ports, the very same place where Irish sea border checks will take place.
The difference? The GFA is honoured, the integrity of the SM preserved, and NI status within the UK maintained.
If this deal doesn't go through, Boris will sign the letter for an extension. He can spin it that his 'dead in a ditch' line was in the context of the backstop remaining as a condition of that extension.
He has got rid of the backstop for Britain, so if MPs dont seal the deal, an extension is asked for, but the EU can refuse, meaning 31st Oct remains the deadline.
An election is called, another request for an extension, an extension agreed to facilitate the election. The election will be about crashing out without a deal or accepting the deal , backstop removed.
If Labour say they can get a better deal they will be trounced. If Lib Dems say they will revoke Art 50, they will make some headway but not enough. The brexit vote will split between Tories and Brexit party, and I think, with the backstop for Britain gone, the DUP will see how precious the British people think their union with NI really is (ie not overly precious).
Boris will win, Britain out of EU, SM, CU.
DUP under a bus.
Then the fun can really begin.