There isn’t a hope in hell that any concession would be made around any DUP only arrangement - none. Any such arrangement would be in contravention to international law. It can not and will not happen.
That said the stakes here are getting very serious. To date I am very satisfied with the robust (EU) support for the backstop and the GFA and don’t see that changing. Any resiling or weakening from that position could have massive repercussions for the whole EU project.
The one unfortunate element in the whole situation is the lack of unconditional support from the US thanks to the incumbency of the biggest moron on the planet.