I'll admit I've been out of the field for a long time... I sort of cut ties and haven't read up on the latest tech in probably 15 years. Your point about missiles receiving mid-course updates is very interesting, though. I have a couple of questions...
Has any (unclassified) work been done on rear-mounted weaponry? I mean, if missiles can have modern CPUs and targeting software, can't the countermeasures have those as well? It seems like accurate, rear-mounted, auto-targeting machine guns (or heck, lasers for all I know) could still be an effective countermeasure, especially if you're in the position of trying to outrun one. That is to say, rather than trying to outmaneuver, outrunning would take you on a straight path, which would put the missile on a more-or-less straight path behind you until it hits. It seems like this is the perfect scenario for auto-targeting defensive cannons.
Lasers have a big power to mass+volume problem for mounting them to fighters. Check out the anti-mortar laser systems for an idea of the size of current laser systems required to shoot down mortars. That's probably a good lower bound on the power required for an active A2A missile defense system. Similarly with using kinetic defense systems mounting a system with a high enough rate of fire along with the tracking and pointing mechanisms just doesn't work on a small plane like a fighter, we have systems like that for ships but they're huge.
Maybe, but at the cost of how much added weight? And even if the thing is approximately 100% effective I'd still think pilots would be very reluctant to voluntarily become a perfect target.
Has any (unclassified) work been done on rear-mounted weaponry? I mean, if missiles can have modern CPUs and targeting software, can't the countermeasures have those as well? It seems like accurate, rear-mounted, auto-targeting machine guns (or heck, lasers for all I know) could still be an effective countermeasure, especially if you're in the position of trying to outrun one. That is to say, rather than trying to outmaneuver, outrunning would take you on a straight path, which would put the missile on a more-or-less straight path behind you until it hits. It seems like this is the perfect scenario for auto-targeting defensive cannons.