Thank you for the advice. As for the group bit, I have a group. I brought it up with them. They agreed with him on the issue. Damned patronizing Solars who get SMA without this kind of work...
As for your suggestions, they give me a starting point to work from. The initial Charms up to the Form are meant to grow from the themes of the Yozi applied to war on a mass scale, plus developing the world-body. Then from the Form it branches out into expansions, each themed to a separate Yozi. Those I have solid ideas for. It's the opening that I'm having trouble with.
Well, if you want general....
(I will point out that a lot of the described effects don't really work well with Adorjan, but I'm including her anyways for completeness sake. Also, SWLIHN gets nothing, because I can't think of anything even slightly appropriate for her. You may want to make it only Malfeas, Ebby, and Cecelyne, or you might want to add Kimbery. Just find an appropriate ranged attack charm and an environmental effect)
The Infernal Native Prerequisites for the Style would be Green Sun Nimbus Flare, Sandstrike Blast, Life Blighting Emptiness Attack Thousand Fold Typhoon Hand, and some kind of easily reachable attack charm for SWLIHN (I'd say Mind Hand, but that's not th one and done attack charm that I'd prefer like the others.) Make it clear in the Style that you only need two of these charms to proceed, to prevent wasted Xp from buying non favored Yozi Charms to get it.
(Also, other Exalt types can't learn these Martial Arts due to the need for a close connection to multiple Yozi that Infernals have.)
After the initial prerequisites, you get a Counter attack Charm that lets you invoke it and use the effects of one of the prereqs you bought as part of the Counter attack.
The third Charm would be a supplemental Shaping Touch Charm that lets you impose your own Primordial Urges on them. If you hit, you choose one of your Yozi Excellencies, and they are afflicted with a UMI Shaping Effect that makes them act along the themes of that Yozi Excellency, with penalties to actions if they don't, and bonuses if they do. You are explicitly allowed (and expected) to lay this charm on yourself.
The fourth charm would increase the range of your prereq charms, and cause an environmental effect related to the Charm. Malfeas blights the earth with Green Sun Wasting, Cecelyne turns it into a Place of Desolation, Adorjan creates a tornado that hurts people, Ebon Dragon creates an orb of absolute darkness where only people with Witness to Darkness can make sight based Perception rolls.
And then finally the Form Charm, which reduces the costs of the prerequisites to 0m (Thousand Fold Typhoon Hand still costs 1wp though. Unexpected is too good for it not to.). After that, it doubles the range bonus granted by the previous Charm, and let's you apply a single attack to a group of people of maximum magnitude equal to your Essence.