My immediate thoughts. (open to much disagreement)
A costly bit of kit, derived from a costly bit of research, that would need to be fitted at great cost to all transport aircraft to achieve the aim. But in reality only of any practical application in designs to come, not those currently in existance.
Against the seemingly very very small chance that it(9/11 style attacks) should all happen again, in the same way, with the same aims.
And yet another level of 'security'. But it is unlikely to displace all the extremes that are in place now.
Also, a response to what happened, rather than what may happen in the future.
let the cake throwing begin.