Muster at the Rally Point

Normally, you want Muster / Rally Point with Ammo Depots. The logic there is you play it like Zarathur -- get rid of cards in hand easy and cheap, and fill it back in.

I love Ammo Depot in Coteaz, but this is not the Coteaz deck to use Ammo Depot in.

What I am considering is dropping either the Psykers or the Tallarn Raiders, for +1 Mystic Warden, +1 Inquisitorial Fortress, and maybe a Captain Markis.

Markis makes sense.

But Mystic Warden? Your primary theme of six cards don't affect him. Why not Taurox APCs? Alternatively, Ogryns are a great choice - they can't be targeted by events, so throwing some choppas on them contributes to guaranteeing that big smack you really want.

I hear ya, but I don't always have/play the cost reducers each turn.  The idea is to either play them first turn if you have the right hand shape, or build your hand until you do - so not every turn is a -2 cost turn.  The cheap units are sort of a contingency plan.  Mystic Warden is great in Coteaz because its (already minor) drawback doesn't come into play.  It can deploy away from Rally Point, it's a good deploy stall, etc...  And it also works as a pseudo-capper because it lets Coteaz command-snipe, which is his biggest weakness.  Mystic Warden doesn't work with the primary combo of the deck in the same sense that Troop Transport doesn't work with the primary combo...  but that doesn't mean I'm going to remove Troop Transport.

So far, they've been about as good in this deck as they are in any other Coteaz deck, although it is conceivable that I could ween myself from the crutch of using them, like I'm working on with Ammo Depot...  We'll see how the deck works after a few more test runs.  And also see if I can keep this deck together long enough and ignore the siren song of Coteaz Smasha Gun with To Arms / Bolster the Defense, which is trying to tempt me to break it apart.

Fair point.

One clever thing with Mystic Warden is his ability to trigger the Formosan Black Ship on his own. That is, wimpier warlords (or 2 ATK warlords fearing you having multiple shields in your hand) sometimes jump to a planet with a Mystic Warden and immediately retreat in an attempt to steal the resources and kill the warden before the planet becomes important.

Since he sacrifices himself, you can trigger the black ship. It ekes out a little more utility from him.