Mac's a great example of what should happen with Swanson. Buy out a few FA years and let him get his big contract elsewhere. We got the best years of Mac and the Yankees essentially paid for it.
Mac and almost all young impact players typically sign away FA years so they can still hit the market at age 30, so Swanson might extend through his age 29 season (1 FA year).
And what will be the cost for that age 29 season? Likely 2x the cost it would have been if he were controlled through arbitration.