Ironblaze

You do get Aura of Chaos, since the Varanguard in Knights of the Empty Throne are heroes with a chaos mark. However, Eye of the Gods is a keyword specific to some of your hero units; the Varanguard do not gain this keyword so they can't use that ability.

That's a big part of it. The Ordinator is a great buff piece if you plan to just park the ships in his aura. However, that's the opposite of how most KO armies want to work; ships are a big mobility tool, and since you can't bring the Ordinator with you, it's hard to get the bang for your buck from him.

You can make most* of those units work well in any City. The Kharybdiss clearly works best as Anvilgard, since that's the only way to make it battleline and to get a Curse on it. I use Darkshards and Corsairs as a core of my Tempest Eye army. You definitely want the Fleetmaster with the Corsairs to buff them (he also buffs the Kharybdiss, so bonus points). Dreadspears aren't bad either, but they aren't the primo melee unit. There are ways to work those units into any of the cities, just a matter of how you want to expand out from there. *Most was indeed a keyword there. The Drakespawn Knights are... Very very bad and there's not much you can do to help them out, unfortunately.

No. To take an artifact from the KO book, you have to be using the KO allegiance. Lethis armies can only bring the Lethis artifacts or the generic Realms ones.

Readercolin summed it up nicely. 1k points of a Steam Tanks army wouldn't be great from a competitive standpoint. I'd also advocate against Living City at that point range, for as much fun as deepstriking tanks is, you can't ambush very many of them at such a small point value. You'd probably get more bang for your buck running as Greywater for the range increase or Tempest Eye for the run and shoot on one of them (or two if you can sneak a second CP in from point-buying or the artifact/spell). However, the other side to this argument is clearly the most awesome Cities army possible at 1k points is: Steam Tank Commander Steam Tank Steam Tank Steam Tank (Insert 150 points of whatever, it's unimportant and lame because it's not a Steam Tank. Cogsmith wouldn't be terrible, nor would some cheap infantry like 20 Corsairs)

With that starting core, you can easily expand into any of the Cities. The question becomes if there's a particular color scheme you like more, or if one of their playstyles is more appealing. Hammerhal is about generating command points and using them. Tempest Eye is generally a Turn 1 alpha strike, moving fast with the saves bonus out the gate, though it also has strong support for a gunline style army. Living City lets everyone be a Shadow Warrior and ambush, great for suddenly making a Steam Tank appear exactly in the wrong place for your opponent. Hallowheart is the Good Guy version of Tzeentch: More spells than you can shake a stick at (and remember as a Cities army, all your Endless spells are always Empowered!). The other three are more... niche. Greywater is like Tempest Eye in that it has good support for a gunline, and is the only city to have extra prayer options for a potential Runelord. However, what Greywater really likes is artillery. Phoenecium is a city that provides easy access to healing and regeneration while also rewarding you if a unit is destroyed. Anvilgard is... Anvilgard. It looks like a Dark Elf/Privateer army, and it does give them battleline hydra/kharybdis as well as curses for them. The downside is their abilities generally just aren't as strong as the rest (and you could probably get more mileage from Darkling Coven/Privateer units in a different city). Anvilgard is probably the only one I wouldn't recommend, but you can make the rest of the cities work, especially with a versatile starting point like you mentioned.

Looking at the Warscroll Builder and the text in the book, it looks like the Knights of the Empty Throne are a subfaction under Slaves to Darkness. The book does say "When you choose a Slaves to Darkness army, you can give them this allegiance instead of any other". You still can't access the regular Slaves command traits/artifacts (because Knights explicitly says you can only use those provided here, no letting a dozen Varanguard share the same artifact realmscape sword I guess), but you still should have access to the Circle option.

Want the terrible idea? A single duradin unit who would just love having access to the command ability making exploding 6s while also not counting against your allies points? Gotrek. You are right though. Most of the duradin support units just buff their own keyword (Dispossessed or Fyreslayers), there's no wizard in the entire race you could slot in for casting, and you can't do cheeky things with Fyreslayers and their Invocations. An idea that might work is having a decently large block of melee dwarves to help sit on and hold an objective or serve as a nice anvil. I've seen the idea of the deepstriking Hearthguard with their leader as a melee harassment tool, maybe hide a ship behind them for nice screened dakka, but I'm not sure how likely I would be to do that over just taking more ships and shooting.

My take on Thunderer special weapons ultimately comes down to what you're doing with them. If they're intended to just sit in the boat and shoot, you might as well go full rifles since none of the special weapon exclusive rules/abilities work while embarked. If you're going to have them get out and camp on an objective, then the specials are likely a bit stronger.

I'm doing my free city (played as TE) as a Cult of Sotek, the idea being when the city needed help the most, it was the Seraphon and not Sigmar who appear. So, they're a bunch of dinosaur worshipers. Most of these were made using spare parts from other kits. Completed conversions so far: -Freeguild Guard are using Saurus Warrior shields, and the unit commander has a Saurus sword. -Handgunners have a banner from the Saurus Knights -Pistoliers riding Terradons with Ripper legs/tail (so they aren't carrying the big ball. Those were a bit of a pain, posing them so they still fit properly as a unit. However, with those flight stands they ended up pretty close to the same vertical height as if on horseback) -Steam Tank made by sticking a Volley Gun and a pair of Helstorm Rocket racks (The kit is three sets of rockets) on the howdah of a Stegadon. In progress: -Dark Riders on Cold Ones (that one is a real pain. Using the Cold Ones from the Scourgerunner kit, but the legs of the Dark Riders are molded onto their horses...) -Freeguild General on a "Griffon". It's a Carnosaur. He also has a Saurus Oldblood/Scarvet shield for good measure. Future plans/ideas: Hurricanum made by sticking the Penumbral Engine on a Bastilidon? Gyrobombers from 'proper' Terradons? More Steam Tanks? Outriders using the Seraphon Cold Ones? Something based on a Salamander/Razordon? Slaan chair into something? There's gotta be something here to work with. Even More Steam Tanks?

Congrats on slaying the skaven!

I would recommend the first list of the two. The utility of the Incantor to shut down enemy casting (don't forget about that 1/game auto-dispel!) is huge, and the Comet pulls double duty as a source of trouble for their wizards as well as giving you a nice block for the Skaven to have to move around, helping you control the engagements and potentially limit the amount of Clanrats that can get into melee at a time. Anvils is almost certainly worth it for the Longstrikes, the ability to snipe out key enemy units is crucial, especially if you can remove the Skaven units that are providing the Bravery immunity/buffs. Suggestion: If you like the Blacktalon model (I don't blame you) and want to use it, I would run her as a generic Zephyros instead of the named character. You aren't playing Hammers, so that keyword on her doesn't matter, and giving her the Anvils artifact makes her an excellent blender to charge in with the Hunters. This can let you keep the Lord-Aquilor by the Longstrikes to use his command ability as needed to redeploy them. In case the Skaven leaders are doing some cowardly tricks like 'taking cover behind terrain'. You could also consider using the Hammernado instead of the Comet. Sure, it's Predatory and everything that entails, but the point difference just between that can buy you an extra command point or set of birds (Plus Skaven are Chaos, so you get the improved MW chance). As a Vanguard player, don't apologize for only having Hunters as Battleline! They are fine units, provided you don't use them the same way you would use Liberators or Sequitors. They aren't a 'stand and hold the line' unit, they're a 'pop up by that hero you hid in the back, time to assassinate him' unit. Vanguard is all about popping up in the places they don't want you and killing the things they left exposed.

Balancing the number of Steamtanks against the rest of your units is important. The tanks and big and can be impressive and potentially terrifying hoard-killers with that main gun, but sheer bodies is what claims objectives and having versatile units is important etc etc. Or... You take Nine Steam Tanks (one commander minimum, with the points to promote three more or include some cogsmiths.) at 2k points. Bonus points for Living City tanks, so half of them are deep-striking. I know which of these sounds way more fun to me.

I played two games (at 1500 pts) over the weekend as Tempest Eye and included a Frigate and Arkanaut Company in it. They proved rather useful for setting up a nice firebase while the Freeguild Guard, Handgunners, and Steam Tanks were walking up the field to the enemy. If you have enough other units to squeeze in three KO units at a 2k point list, I could see a serious use for an Ironclad, Grundstock Thunderers (ideally all with the standard rifle, of course) and an Aether-khemist to send off to capture/hold an objective on their own.