So the precursors spot your thermal sig, start closing in, but can't get a lock with active sensors so don't start firing. Then you unload the tubes on them. Cool ship, although the armament is pretty light, and some of the larger precursors might shrug it off and run you down. They'll be able to lock you with their anti-missile actives, which will probably pick you up and not much less than 15mkm.
I like the strategy, but maybe going for 25-30mkm missiles would be better? Remember that res 1 sensors that can pick up a size 6 missile from 2.5mkm, like the ones I've seen precursors using, can pick up anything 1HS or larger from a lot further than that.
I've had a try at something similar, using FACs with box launchers escorted into system by a survey ship as an early-game way to deal with small groups of precursors before I have a proper "blue water" navy.
It's pretty similar to a WW2 submarine.
You can control the bait, your thermal signature, by regulating engine power. The
Shinobi has a signature of 80 only at full power, so it can easily be stealthier if you're willing to go slower. The armament is light, yes, because the ship's essentially an armed scout with very strict tonnage limits for the sake of minimal TCS. Admittedly, I only got to use it against the smaller kind of Precursor vessels, but in that case the
Shinobi could remain undetected in the face of active sensors as close as 8 million km. Wolfpacks could possibly take care of more/larger targets.
What'd be the advantage of longer-ranged missiles? They'd be bigger unless performance's reduced in other areas, and that would have a detrimental ripple effect across the whole design: enlarged sensor suite, bigger launchers, less magazine space and heavier, slower final hull and therefore more noticeable cross-section. The
Shinobi is meant to and can draw targets in close, and the less distance between you and the target, the less time you give the enemy AMM point defense.