I've no idea how you'd do this in JOSM.
I've undeleted the old nodes, ways and relations that were deleted in error and redeleted a couple of ways in https://www.openstreetmap.org/changeset/137766612 .  I think that's everything now; although some of the objects referenced in https://www.openstreetmap.org/changeset/137720979 perhaps could do with another pair of eyes.
