This is story is really both tragic and hard to believe.
That being said I think we have to recognize that it would be tremendously complex - if not impossible - to setup a system that would prevent a repeat with a high degree of confidence. Simply put if a pilot wants to crash the plane he can do it. Yes some protections could be put in place but they would create new issues by themselves - on a pure risk / reward / cost analysis I guess the best action is to do nothing I leve with the (thankfully) very very low risk of another such atrocity.