Jackson isn't a replacement for Meek or back up for Darcy, he's Lobb's successor. Jackson is a 199cm ruck/forward who is incredibly agile and athletic while willing to fly for big marks and be first up to crumb the spillage. He'd fit perfectly into a pressure forward system while rotating into the ruck to give Darcy a rest when needed.
He'd cost probably our first pick at this and next years draft but when those picks are likely to be after 15, that's a steal. It'll probably take a player leaving too (Lobb/Meek) but that'd still be a win for a 20yo rising star. We have established young talent in the squad and so adding more at the draft is not necessary any more. We are beginning to challenge with plenty of development left in the side so now it the perfect time to top up. Picking up a 20yo who is far from anywhere near his high ceiling talent wise is a fantastic move and improves us for the next decade.
Ignore Sumich's figures, $700K/yr is market price for the most promising key position forward/ruck to be seen in a decade. Especially when that's a hole in our list moving forward (Lobb is 29 and while a gun, not here forever). If we get the deal done, we're laughing.