The trouble is, Boris, Nigel and their Brexit wrecking crew have just gone and proved de Gaulle right- everything he said about the UK being a disruptive force trying to upturn the European project has been vindicated by history. It’s going to be a long time indeed before anyone can trust the UK to stick to any sort of diplomatic agreement (including international law), now that the current bunch of spivs and wasters in charge have burned down the UK’s reputation to the ground. Who would enter into any sort of agreement with a country that makes it this clear that it will renege on any agreement it likes for temporary domestic political advantage. It’s just a matter of trust.
If the EU wants to help the people stuck on these islands, the best it could do at the moment is to revive the proposal for separate EU citizenship for all those of us who have had it taken from us.