I applaud your positivity in that we should have these extra security measures in place...I also assume you're of the firm understanding that these do not come for free and require upkeep, hence the most practical (actually, probably just the easiest rather than most practical) model for instituting such modifications would be to pass on an extra cost to the passenger. (Should also add that with the exception of government owned airlines - and even then - apart from regulatory approval or compliance there would be no compunction on the part of governments to oversee the installation or funding of such measures).
I'm not saying the idea has no merit, but I know at least one person on this forum is not going to spend another dollar on air fares even in the name of security (no, I am not it). People - including the commercial sector - will start to find reasons to justify not installing such systems, particularly alluding to the risk assessment processes which will likely be more probablisitic than (pragmatically or not) risk adverse.
Let's also be clear now that this discussion is only more prevalent post facto MH17. This is not addressing or criticising a particular blatant/negligent failure of procedure previously (again, working on predominant current theory and information).