I would do that trade.I'd expect they would take pick #1 to 6 for Kelly and pick #13 to 18, that would be how we got a package of later picks too.
Unfortunately Geelong don't have a 2nd or 4th rounder of their own next draft, but they do have Richmond's third (#54ish) and Carlton and Gold Coast's 4th round picks (55-60ish).
So best case for Fremantle that trade looks like:
#6 for Kelly, #13, #54, #56, #59
Then we draft Ian Hill with #13 and get to argue for another decade over the talls we overlooked giving up that top ten pick.