I've been assuming that the "solution" to stopping Pan was to force him to grow up.I'd like to see Pan exiled/sent somewhere and then return to the show in a year or two having begun to 'grow up' outside of Neverland.
But the introduction of Pandora's Box was an interesting, unexpected choice.
As I recall per the classic story, what's left in the box is "hope", which is indeed potentially the most powerful weapon of all. Is Pan doing what he's done because he lost hope? Will Rumple restore it to him via the box? Or is that too on the nose for this show?
I think it's likely they intend to trap Pan's 'evil' within the box, be that the person, or some evil essence in him