Well thats mostly my point. This DL is a mess. Adding Peppers and Melton will help, but doesn't get us to where we want to be. This is a multi-year DL rebuild, just like the OL.
All it takes is one young stud to make a huge difference. The DL can be a quality unit as long as you have competent starters everywhere else who aren't in their 30's. In that framework, Peppers fits as a rotational piece who plays mostly on passing downs. I also think Crawford comes back given time, but only as a rotational piece on the strong side.
Even still, 1 rookie (RaShede Hageman or Aaron Donald) and 3 free agents (Melton, McClain, Mincey) with the average age plummeting already is a massive change from last year. Selvie, Crawford, Bass, and Hayden are young enough where there are fewer downs with players taking plays off. It lacks a true pass rusher, though the combination of Melton/Donald essentially becomes that guy by scheme.
2 rookies (Kony Ealy, Will Sutton) and 4 free agents (Melton, Peppers, McClain, Mincey) essentially rebuilds the whole thing for years to come. You have instant/future inside pass rush (Melton/Sutton), outside pass rush (Peppers/Ealy), and LDE play (Mincey/Crawford) with Selvie and Bass/Hayden as rotational guys.
It would be hard to get both Melton and Peppers for Dallas, but one of them should be do-able. If Dallas can't get Melton, then the priority shifts to Aaron Donald in 2014 and future RDE in 2015.