The question I have is: can you scale down the well-guided missile? I thought guidance is mostly an issue of fast chips and well designed software. But perhaps you need big missiles if you want them to fly fast and have a lot of range.
Talking about anti-air of course. Lots of small missiles aren’t going to be effective against hardened ground targets.
Sensors matter a lot for guidance. In order to build an effective radar guided missile it needs a fairly large array. So in practice the minimum missile diameter ends up being something around 7 inches. Long range surface to air missiles have to be much wider than that.
Data links also make a big difference. So the missile needs another fairly large antenna to receive guidance cues from other platforms.
But perhaps you need big missiles if you want them to
fly fast and have a lot of range.
I'm just a layperson but this has always been my understanding. Modern air combat is all about firing from beyond visual range, so I think they optimize pretty strongly for that.
See my other answer, though - air to air missiles ARE generally (always) proximity fuzed. They don't need to precisely impact the target, they just need to get close.
More then that, air-to-air missiles generally are designed to blow a load of metal shrapnel through whatever they "hit": so there's a problem where if you're fleeing from a missile and it explodes behind you, even though it "missed" the payload can still hit the plane it was chasing if the plane doesn't change trajectory.
Talking about anti-air of course. Lots of small missiles aren’t going to be effective against hardened ground targets.