Yep. You can make turrets faster than the listed tracking speed, you just have to put more volume into gears. Tracking speeds much below 20,000km/s will get you slaughtered.
At your tech level mixing and matching different weapon types just chews up space. Drop the 12cms and their fire controls, turret the 10cms, and tack on armor. Useful anti-ship active sensors are always going to be laughably oversized; just make a dedicated spotting ship or two and stick R1 AM sensors on your combat ships. Don't bother with EM passives, thermals will pick up enemy ships, populations, and missiles just fine, and the extra space will let you armor up more.
Use multiple small reactors instead of one big one, especially with ships this slow and thinly armored. One lucky hit will completely defang one of these. Don't worry too much about your speed, TL1-3 ships never go anywhere fast, and your fuel limits you to a range of ~2-3 systems anyways.
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Basically at this point in my campaigns I don't even bother building anything more than disposable FACs to keep larger colonies happy. If you run into Precursors at <TL4 there's not really much you can do apart from avoiding them. If you run into Star Swarm it's basically just a matter of praying that they avoid Sol until you get your tech up and crank out a couple long-ranged fast laser cruisers to pick them apart. If you get Invaders at anything below ~TL6/massive fleets of TL4-5 ships spamming thousands of missiles and meson beams you're just straight up fucked. Even a freshly spawned NPR will usually have better tech and more ships than you. My advice above the level of improving the ships would be to focus all of your industry on surveying, mining, bootstrapping your industrial base, colonizing, and researching.
is this game still as ridiculously obtuse as i remember from years ago?
The answer will always be yes, and I hope it never changes.
Thank goodness for that. The market's already saturated with streamlined 4Xes.