The rules are complicated in an uncapped year - it's not a total free-for-all. There would be a limit on how big a contract a player can receive: I think it's about a 25% increase over his last one. Also, playoff teams can't add that many additional players - the top teams can only replace players who leave through unrestricted free agency. Additionally, you would need at least six years of service to be an unrestricted free agent, meaning anyone drafted since 2004 would play by restricted free agency rules. Peters would be stuck. Ditto Edwards, Butler, Hardy, Parrish, Williams, Lynch, McCargo, Puz, DiGiorgio, Whitner, Simpson, McKelvin, Greer. It won't doom us, it would just be a huge, ugly mess for the league and the players.
That's why it's there - to make sure there will be no uncapped year.