There's two problems with your first idea. The primary issue is that such an interceptor would need to be more expensive and more capable than the missile it's

There's two problems with your first idea. The primary issue is that such an interceptor would need to be more expensive and more capable than the missile it's gonna hit, not even taking into account all of the supporting infrastructure necessary. The second issue being that if you're going to be operating near (horizon distance, so let's say 200km) of a missile launch site, you're going to be bombed or missile'd to smithereens. If you can prevent that, you could just bomb the launch site to begin with. As for interceptors fired down from space, you'd need to expend all the energy to get them into orbit, and then expend the energy to get them back into atmospheric flight, which itself is going to be 10x more expensive than it's target. There's also the issue that while in suborbital flight, the hypersonic missile can just adjust it's trajectory a bit and the whole trajectory is now useless.