I do think that could be the wrinkle. The object Robin holds most dear wouldn’t necessiarly work for Nealfire because he has no sentimental attachment to it: but the pendant…! Given his speech to Mulan in 301 about how not going after Emma was the greatest mistake/regret of his life, using the pendant she wore for over a decade and gave back to him would certainly have value to him emotionally.
but it would involve using one of Robin Hood’s most precious possessions. I still think it is the Bow and Arrow, as for the wrinkle how do they aim it to get to Emma or something like that.