Think I would combine air touch techniques, low lighting the shorter pieces left over, which will give you that depth towards the top and blend the colour nicely through the mids, baby light and balayage, maybe teasing a bit to retain any natural depth towards the top...how that darker section will lift out tho could really limit the outcome.
Then zone tone appropriately to increase the blend and achieve the cool tone. Maybe a 7 towards the root working your way up to a 10 on the ends.