So, to get it out of my head, here's where we are...
Nowhere near agreeing anything on Northern Ireland. Without this we crash out in March. Doom.
(I'm now coming to the conclusion that Chequers was keeping us in the common market for goods as a solution to the Northern Ireland border. I can't think of any other explanation for thinking it might be a good idea)
Trading agreement (dependent on withdrawal agreement):
Labour will only vote for membership of a Customs Union.
The ERG faction of the Conservatives will only vote for something like an FTA.
SNP will vote against Chequers.
Lib Dems will vote against Chequers.
Chequers therefore cannot pass, because Labour+ ERG+ SNP+ Lib Dems is a majority.
And in any case the EU have said it's impossible, repeatedly.
Theresa May says she'd take No Deal over an FTA. So that's not getting through without replacing her, which doesn't look doable to be honest. There are numbers to call a vote, but not enough backing for anyone else to replace her.
So either we get the snap election there's been rumours of, we get a referendum, or we fall out with no deal.
Have I missed anything?
(I think this keeps going round in my head because I'm trying to think of a solution. That's what my brain when it sees a problem. Keep turning it over in the background to see if it can see any viable options. Sadly there are no clear escapes from this trap.)
Original post on Dreamwidth - there are comments there.