Backstop par is intriguing and ambiguous 
What UK means by backstop par will be crucial to unlocking a deal. Worth remembering that to get to March 2019 with an exit deal and transition, the backstop is key. On future, a political declaration will suffice.
Aspects of UK plan will be problematic for EU27: clash with integrity of single market (the one fundamental EU red line). Pars on ECJ/EU law will probably require more clarity too
But understand, EU27 will welcome, it's a start, in the knowledge that all the details of the future relationship don't need to be agreed now – there could be more loosening of UK red lines in future
May seems to have conceded very little compared to what was briefed during the week. Concessions are mostly aspirational - TPP reference the best example of this
Playing devil's advocate, if May's plan was to get to a softer Brexit step-by-step, the PM has a few –big – steps to go, and may yet fall, but the direction of travel if you compare tonight's statement to her early speeches is quite clear
Finally, reposting what an EU27 official told me weeks after the referendum: if we agree an off-the-shelf option, the UK will want to call it a 'special British deal'
