Great stuff! You really know how to break it down. You've put into focus all of the things I've been tinkering with in my head but just didn't have any perspective on.

I think the reason why I want to explore Shadowrun again using AW is to focus on the psychological trauma of having, in a period of less than half a century, cybertechnology AND magic becoming solid features in our world. Having said that, the loss of Essence by gaining cyberware isn't a huge deal thematically (like you become a colder, deader person or whatever), unless it's affecting a magical character since Essence is the connection to magic. That goes into the magic system of SR, where some spells target a character's Essence (i.e. a healing spell is harder to cast on a low-Essence character). For me I suppose it's a pretty mechanical feature overall.

Let me try to answer your question of what do I want Essence to do in my game.
"Essence will power the magical abilities of awakened characters and indicate the metaphysical wholeness of characters, both awakened and mundane."
So I guess three things:
• power magical moves
• gauge how much chrome a body can handle
• indicate how susceptible to magic a body is

I wouldn't bother with both Magic and Essence.

I was already on to this. For this type of hack, I see the moves as ways to cover the different skills from SR. So there will be conjuring, sorcery, etc moves, all based on the intrinsic power (Essence) of the character. And then Initiation will be a move that can be taken after the character takes a certain number of other advances.

Essence and Synth might either always sum to 1, or perhaps the combined totals could never exceed 1. So if one is +2 the other is -1, if one is +1, the other is zero.

I like this a lot, I was just having trouble with the balance. But then it changes what Synth means. In The Sprawl, it represents your ability to control and be at one with the chrome, right? In Shadowhack, would Synth go up when you gain cyberware? If a non-cybered character gets a piece of cyberware, his Essence goes down but does his Synth go up? And then, if he gets another, and it goes up again, does that represent not only that he has more cyberware, but that the more he has, the more he knows how to use all of it? I think I'm cool with that. It's just another sort of "wholeness" I suppose.

By the way, I love the hunted/owned/unreliable cyberware stuff you did. It makes the whole thing so much more scary and intense.

I saw in a post from a while back that Synth is on the chopping block? Any news on that? I think it's a great way to deal with cyberware but I'm eager to see how you'd do it differently. I'm actually gearing up to use The Sprawl as a basis for a Shadowrun hack, and I'm trying to figure out how Essence and Magic would be affected by cyberware and the Synth stat.

No problem! I don't think myself or Nerdwerds was saying anything bad about anyone's work or choices. I value everything I read by everyone who contributes, it all helps, it's all inspiring.

One thing I will say in favor of using the elements versus the other style of stats is that- at least for what I'd like to accomplish in the Oriental Adventures-style hack I'm working on- it adds a different flavor, something more cosmic I guess. Especially if they fluctuate instead of certain stats advancing. It depends on what you're going for. I'm going for something more cosmic and poetic, where others might be looking for something a little more crunchy and detailed. Certain things don't have to line up perfectly, that's what hacking is all about- to get your own game out of it!
A bit of my story:
I started doing a lot of work hacking the original Oriental Adventures setting into Dungeon World. It was pretty straight forward for a while, I just cobbled together the different moves for the different classes that corresponded, and added new ones that reflected different unique things in OA. The classes were samurai, shukenja, wu jen, kensai, bushi, barbarian, ninja and yakuza, and there were a few different races. Then things got a little sticky, because there were cool things that I wanted to add, like the proficiencies from OA/D&D, and the honor/family system, martial arts, psychic duel etc. I wanted it to be innovative at the same time as being classic and faithful to OA, but I couldn't do all of that and have it be as elegant and comfortable as DW without making a lot of revisions and changes to the system. I thought that using the elements would be a really cool way to do the stats, but I eventually just set the whole thing aside to work on other stuff.
I just started thinking about it again but in simpler terms. Making it more of a "mythical Japan" setting rather than a L5R or Rokugan hack (but still being inspired by the original classes and stuff). Lone Wolf and Cub is also a big influence.
For me it would be less about the customization and options for all the classes and more about how those classes deal with honor, duty, mysticism and the other classes. Basing it off of AW instead of DW was a better way to go, so I'm starting in again, glad to see you guys are working in the same realm.

Hey, I'm sortof doing a similar thing, I'm working on a pretty straight-up hack of Wraith: The Oblivion into AW. I love the theme and intent (and art direction) of Wraith, and I love the Apocalypse World rules, and think that they could really make the Wraith thing pop. I'd like to hear how you're making out, if you're still working on this. One main thing I'm puzzling out is the Pathos/Angst/Shadow concept, which is similar to the Humanity/Beast part of Vampire. Maybe they could run on the same type of engine.