I really like symmetry, so I would remove the left strip from the right-hand section and reproduce the left section from right to left. Then I would take the section that you removed and put it into the center where it's set off by the two of the sage strips.
As for borders, maybe a ribbon border on the sage green using all of the colors already in the quilt? By the way, I really like your color combination. Looking forward to see what you come up with!