These particular rules cannot be changed because they are too much at the heart of the league (in my opinion). People have based their initial strategy on those rules.
Four, or five at the start of this finished season, is a very long time. If those players all are still very productive, those managers will probably try to trade those players for players with different contracts (at least that's what they should do). There are lots of years left to try to get a good deal. In this aspect it is no different than when teams in the nba can, for one reason or another, not re-sign a player > see Harden, Williams, Howard or ... Bosh.
If you want to make sure you can keep your good players you have plan ahead, the cap is just low enough that you have to make some choices here and/or have to be active in trades and high enough to be able to keep a lot of your core for a very long time.