I have been advocating central locking of overheads for several years now, as it would provide the only guaranteed means of stopping pax retrieving bags.
I guess one question is whether that would actually be safer. It might guarantee they don't get their bag, it doesn't necessarily guarantee they'll get off faster or more safely.
It could just mean you'd have a bunch of people struggling trying to open overhead lockers and getting in the way of others rather than moving down the aisle with their bags...
It's one thing to try and design better systems, but they need to accomodate how people actually behave, not how you'd like them to.