I was thinking of the days of Reggie White/Vonnie Holliday as power ends in the 4-3 and thought maybe Wyatt and Brooks could fit that role, especially on early downs. But you are probably right, times have changed and guys have to be freaks like Reggie to pull it off now. But I do think Hafley must have sold it as the guys we have are better fits for it or we wouldn't be changing. Just start with stopping the run, I think that part is still considered a strength of the 4-3.
The switch does require another LB and unless we score someone in FA(Devin White?) I expect one of our top 3 picks to land a starter there.