The NFL needs a reverse Franchise tag .. they could call it the ... Disenfranchise Tag!
By using the "Disenfranchise Tag" it would allow any team to release a player and wipe their salary off the books for a one time fee based on the average salary of the top 5 paid players in the position over the last 5 years (the same as the franchise tag).
That way there would be a one-time cap hit, no future dead money and the player gets to leave and continue his career and the team gets to save some money and move on.