Do some war veterans suffer from CTE in the same way seen in boxers and football players? Perhaps and certainly not good if true.
Current work seems to indicate that there is no way you can build a helmet good enough to protect football players. You don't need to be knocked out, but rather smaller accelerations of the brain against the skull produce an additive effect.
It would be easy to build small accelerometers into helmets (they cost less than a buck and the supporting electronics could be inexpensive) and I suspect we'll see them soon. Carefully calibrated devices that would give evidence that could be used in a courtroom would be much tricker, but I suspect the threat of lawsuits over CTE and a few successful cases at the NFL or college level will kill tackle football in high schools around the country (except for Texas where it is a religion) within ten years. No one is going to be able to live with the liability threat in the long run. There will be rules changes, but will a game that doesn't produce head trauma be acceptable as public spectacle?