Would this really solve anything? It would reduce the rate of serious hits (and thus concussions). But by what amount? Any time you have men this size, who are this motivated, moving this quickly, you'll have serious injuries.
Not to mention the fact that the elephant in the NFLPA's room is that its starting to look like subconcussive impacts are a major part of the problem. The big hits and helmet-to-helmet draw the attention, sure, but the 60 hits per practice are what drive much of the damage.