I'm going to insist on what I said in the other thread: the "deal" is the withdrawal agreement plus a political declaration on the future relation and a transition period to negotiate the future relation. And the withdrawal agreement involves money, citizens, and the Irish backstop.

Under your scenario, with the DUP out the window and a Labour/LibDem/SNP majority, the deal Corbyn may be forced to seek is special economic status for Norhern Ireland, Gibraltar... and possibly Scotland and Greater London. One country, five systems. The EU would grant the devolved governments of the UK and its crown dependencies and overseas territories special arrangements as exist for other microstates and peripheral regins. And the customs borders would be within the UK.

Would that pass he Commons? I doubt it. Corbyn would probably be assassinated. And it wouldn't pass a referendum due to the English vote, I don't think.

A society committed to the notion that government is always bad will have bad government. And it doesn't have to be that way. — Paul Krugman