The problem with this logic is that you have to maximise the value received in return for the potential franchise players you let go. We failed to do this when we lost Gunston and Bock. We miserably failed when we lost Tippett. We're still paying the price for these failures now by being out of the finals in 4 of the last 5 seasons.
If we were going to roll with the Tex, Sloane, Talia, B Crouch quartet, we HAD to trade Dangerfield at some stage in the last 14 months. While Danger would never have agreed to a trade to Melbourne, something definitely could have been worked out with the Pies (pick 5, someone like Sam Frost and some gravy on top of that) or Cats (picks 14 and 21, M Stokes and G Horlin-Smith).
Losing him to free agency will net us something like Pick 13 in the upcoming draft. This would be an unmitigated disaster.
I'm far from convinced that he'll leave, but make no mistake, if he does leave, it's going to be a massive hole that we need to climb out of.
The difference in afl free agency is that clubs don't have unrestricted trading of players. Quite an incredible oversight by the afl in the last collective bargaining agreement.
The result is the club cannot simply trade a player to maximise their return two years or a year early. The player must agree to the trade.
This Gives ALL the negotiating power to player. The club simply cant negotiate the way you are describing. Put yourself in dangers shoes in the offseason. Further lets assume he actually is looking to win a premiership and get paid rather than simply go to the highest bidder (as he seems to be implying).
If danger wants team success at his next club it is in his interest not to agree to a trade. In your example it is better for him for the pies to keep their picks, top up elite talent and let the Pies play them for a year before he gets there. He then joins at the end of the following year on big money to a more talented new club with a better shot at the flag.
It also gives danger 12 more months to check out the moves at those new clubs. A change in coach and other free agent signings could also lead him to think hawthorn or richmond are a better fit.
I suspect this is the scenario we are actually seeing be played out right now.
All the club can do it has done. New coach, new ceo, likely chasing free agents itself. Saying we should have traded him in the offseason is nonsense for the reasons outlined above.
If he doesnt want to re sign he has all the power.