My suggestion would be a force of cheap, disposable FACs (or small ships if you haven't researched FAC engines), each with a number of box launchers (or the most reduced-size launcher you have researched).  Design a missile that goes as far as the precursor missiles can reach and has enough spare fire-control range to account for their ECM.  Give the missiles small active sensors in case the launch platform is destroyed before they arrive. Make the missiles small, size 3-4 or so, but with at least Damage 4. Fire everything you have as soon as you can, all at once.  Aim for at least 5 missiles per 1000t of precursors, and split what you have among their fleet. Blow your entire load in one volley, so to speak.  

Your doctrine for this engagement is "At least they'll die too!"

That's exactly what I was working on, actually - since it's the very next system, and I don't even have to put much fuel capacity on them.  I'll have box launchers in 18 months, and their missiles are apparently VERY short range.  That, or their sensor resolution is set VERY large, so they have trouble seeing my ships.

Be aware, though, that precursor squadrons often operate near a robotic listening post that contains a large ammo dump.

My suggestion would be a force of cheap, disposable FACs (or small ships if you haven't researched FAC engines), each with a number of box launchers (or the most reduced-size launcher you have researched).  Design a missile that goes as far as the precursor missiles can reach and has enough spare fire-control range to account for their ECM.  Give the missiles small active sensors in case the launch platform is destroyed before they arrive. Make the missiles small, size 3-4 or so, but with at least Damage 4. Fire everything you have as soon as you can, all at once.  Aim for at least 5 missiles per 1000t of precursors, and split what you have among their fleet. Blow your entire load in one volley, so to speak.  

Your doctrine for this engagement is "At least they'll die too!"


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Edit re below:  Good point.  I hadn't thought of that. Spoilerfied.

So, from what I've experienced so far, Precursor ships have no maintenance issues, never run out of fuel, and never run out of missiles... is that right?

Because, man, after all the bloody freighters they've destroyed over the past 10+ years (after my neighbor opened up trade through a precursor system), they sure don't SEEM to have a limit...

I think I'm going to have to actually get rid of them, just to keep my stupid STUPID civilians alive.