Would it make sense for the UK government to state that the Northern Ireland/Ireland border can stay open permanently on two conditions:
1. Ireland stays outside the Schengen Agreement and,
2. Ireland undertakes to act responsibly in not allowing people or goods to pass through its ports if they are clearly destined for the UK and are seeking to avoid UK immigration or customs. In this case we would give similar undertakings to Ireland.
Neither of these would place any significant burden on either party and the arrangement would only come under threat if there was a clear, substantial and otherwise unjustifiable increase in the movement of people or goods in either direction.
The major objection to the current deal goes away - no backstop.