I read that UK has offered a pared down trade agreement, but as far as I was aware we can't discuss future relationship until after WA. So my theory is that it could be with Ireland, maybe rolls over the GFA and replaces backstop in the WA
Backstop was an insurance policy for UK, if UK couldn't fulfil obligations to Ireland. If UK and Ireland get a deal, Ireland can protect it's interests if EU are unable to negotiate a deal. EU members have ability to sign trade deals, much of Ireland & UK trade could be protected, expanded if no trade deal with EU was possible in transition and it would be up to Ireland to protect SM
EU said they wouldn't discuss future relationship until WA is done, but the obvious solution to a border is a treaty. There is some strange contrasts when you go from talking about frictionless trade and FoM, then demand an iron curtain and borders of which no combination of cameras, drones, blockchain or other technology can ever truly satisfy. We're a couple of islands, easy to do checks at ports, theres a lot of water that provides frictionto rest of the EU
UK, NI and Ireland are all on the same page of no hard border, it becomes increasingly problematic for EU to push for a wall, with checkpoints, sharks and helicopters, but also means they have minimal leverage on future relationship, as UK would already have limited access to SM by default by end of 2020 or sooner with no deal
EU wants to retain full access without balance, as they doing very well out of it, but ultimately they would have to open SM to UK's sexy low tax, low regulation bonanza. So think most likely outcome is a balanced pared down trade deal, but I suspect that they might realise they are on the clock and will be working overtime to extract as much as they can, but now think WA will pass before deadline and without major extension