It would be completely unnecessary in the NFL. The NFL in itself offers another possible model. And it's a model that would be just as difficult for other sports to follow.
Something definitely needs to be done in Basketball. I see two teams right now that can field rosters that seem complete and balanced, and one of them is filled with players heading towards retirement. Sure there are quite a few that are close, but that's still a big downgrade over the NBA that I remember. Close only promotes so much interest.