I was thinking of a new class of 3 stage missile, about 16 MSP. Part one is basically the largest missile engine possible, about 5 MSP, and 1 MSP of fuel (adjust to your preferred ratios, and power level on missile drive)
Stage two is 2-3 MSP of sensor, a stationary "mine", but with a much larger sensor head and therefore engagement range
Stage 3 is 6-8 1 MSP submunitions, with the highest power setting available.
The reasons for doing it in three stages, instead of putting the sensor on the first stage, is because that big sensor will reveal it, and therefore the location of the launching ship.
The idea is for it to launch from outside of enemy AMM range, because fire controls are unlikely to be able to lock in to a 40 ton missile, (down to 25 by stage 2), unless you have AMM that home in on EM.
Obviously, you are not going to get a great rate of fire or volume of size 16 missiles. But you could put them in box launchers for a stealthed carrier, where the fighters basically launch their missiles and get right back on the carrier, because stage 1 will just go to the last location targets when the fighters get back on their carrier.
This weapon deals a fairly significant amount of damage at a huge range, because the final stage swarm missiles are really fast and small. However, there is inescapably overkill issues unless the final stage swarm missiles have a sensor too. Doctrine wise, you lose a LOT more payload per missile for small missiles having sensors compared to larger missiles. But for something that operates like a mine, perhaps the final stages HAVE to have some sensors no matter what.
So tactically and strategically, what sorts of counters are there?
Detecting the missile in its stage one phase seems impractical, maybe if you have a sensor platform close to the enemy when they launch, you can vector some fast fighters with AMM to take them out.
Stage 2 can be detected by seeing its emissions, but chances are it will already be inside its range at that point.
A lot depends on where it is being used. In a warp point fight where the targets are on the warp point, jumping out is an option. Just jump back in outside of the myopic sensor ranges of the swarm. So defending a warp point with these would be problematic vs a human player.
Might be kind of fun to station these defending a warp point from the attackers side, because they are fire and forget. Launch and retreat, using them to damage an attacking force without much fear of being damaged in turn, at the expense of conceding the attackers' side of the warp point.