I was thinking about anti-missile ship designs, one had lots of box launchers to deliver a huge number of anti-missiles at once, if needed. But then I thought, how about anti-missile mines?
Have the start stage with the reactor and sensors, and because you might need fairly big stage for the sensors, have it have several counter missiles in its second stage.
You could then have the capacity to quickly deploy enough anti-missile capacity to soak a large volley, if you are talking about protecting a planet from a small mobile force.
That's an interesting idea. I don't see any reason why it wouldn't work, although you would need a large first stage to accomodate a powerful enough resolution zero active sensor to spot the missiles far enough away to launch and intercept in time.
Steve
One of my thoughts was how to do a "quantity has a quality all its own" philosophy. A fleet design with rather large magazines could prefire a lot of missiles. In a confrontation that they arranged and prepped for, they would have an outsized punch. Of course, once they launched all those missiles they were sort of committed, because it would be rather expensive.
So a defender might think, "Oh, they are at 7.5 million km. They might launch some missiles, but anything with this much range they would only be able to large a small volley size." But the attacker has a long range, fairly slow, stage, allowing all the volleys to meet up at a waypoint. So all the 2 stage missiles meet up at say 2 million km, and then go to their higher speed stage.
Similarly, a defender with that design philosophy would be tracking the attackers with colonial sensors for a long range. They might have ships move slowly into position, tossing out pods, er, 2 stage missiles. Of course, if the attackers detect the missile launch and run, the defenders have shot their bolt. So having a stealthy scout with sensors that can spot missiles a long way off would be kind of useful, to provide warning of oversized missile volleys.