[Suicide Junkie]

Part of the overall AI weakness you are seeing is the fact that you are playing a sequential turn game.
AIs are hardcoded to treat it as simultaneous all the time.

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The game is intended to involve trench warfare, but a fleet of Planetary Bombardment missile ships can either chew through it or soften the enemy up before your invasion.

About the size/number of components, I think you've got it.
#2 and #4 are your design tradeoffs. You can pack a bit more in, or you can make it easier to repair. And the large engines are much cheaper in resource cost too.

They are indeed pretty slow for open combat, but open combat is pretty hard on all the weapons.
Big densely packed fleets make all the weapons more effective; the targets won't be able to evade or run, and there will be a lots of targets to choose.
Choosing a strategy that spreads your fire around is also very important. Because of the leaky shields and armor, crippling an enemy is much easier than destroying them; 2 or 3 disabled enemy ships means less return fire than 1 vaporized ship. This is particularily so with missiles since they tend to overkill a ship.
I think I will increase the speeds by 1, however.

The size of the armor is not the important part of making plasma cannons more useful, but rather the shielding.
Strong shields can block most or all of a DUC shot, but plasma has almost double the punch.
Still, plasma is the least commonly used weapon. It does make an effective anti-planet gun; high power and no ammo means you can leave the ship in orbit to rain down death for as long as you need it to. The low accuracy is mitigated by the fact that there is no ammo needed and all the time in the world to blast away.

The AIs are indeed mostly the same. The only major differences are what culture they choose at the moment. Rollo should be around again this fall to finish up the AIs, I believe.

One on one engagements with a warship vs a PD ship are clearly one-sided. Even if they did fire, PD guns would bounce off your shields harmlessly and merely waste ammo.

I find that the AI tends to blockade a planet and send down suppressing fire while they bring in their troop transports. If you don't push them off fast enough, they'll eventually take the planet. And if the planet is undefended, they'll wipe it out with DF and move on. Not bad for an AI.

And as for training facilities, it is known that the AIs can't be made to use training except by blind luck. The training is quite slow and limited, which mitigates this somewhat.

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Having defeated the AI, how do you feel about taking over an empty slot in a PBW game with real humans?

"Carrier Battles #8" and "Carrier Battles Deluxe #2b" both need one more player to replace Axel, who is doing well but got kicked in the head by real life.

It should be noted that these two games both are using older versions of the mod.
- CB8 uses v1.3e, which has oversized carriers (400-1000kt) and a different missile scheme, among other things.
- CBd2b uses v1.4a, which has a faster missile scheme and lacks some of the latest features such as AIs, logos and ruins.

Both games are at their peaks, with big empires, large navies and plenty of battles involving hundreds of ships.

PS:
I think the slow missiles in v1.6 may have been left over from when I was trying to fit a "missile propulsion" tech into the mod, which would increase their speed; 2 and 3 being the base low-tech speed.
I'll make a few more tweaks and release v1.6b soon.