47 goals doesnt have to come from 1 player. Lets say, 30 from Weid, a full season from TMAC might net another 10, Spargo may kick 20, Petracca may improve his goalkicking, Gawn may rest forward more with Preuss etc. We may lose some firepower, but we may also strengthen our backline, we will find a way I'm sure.
NAB contracts are 2 years from drafting but can be broken, Schache is the most recent example from memory who signed an extension then was traded shortly after, so Cerra can be in play if my research is correct.
Correct me if I'm wrong but Danger was a free agent and Geelong didn't need to give anything up, at Dangers request he demanded that Crows were looked after, so they were given draft picks.
I also hope that in the back of Jesse's mind, he respects and demands us getting maximum value for him considering how the club have treated him through all of his issues since day one, I hope he says to Freo, I want Melb to be looked after, much like Danger did with the Crows.