I'll start off by saying that I agree with you 100% about two Orders not sharing a body focus. I was suggesting that maybe one of the Inhalation and Exhalation Orders are tied to the diaphragm, and possibly the other to the lungs, probably Windrunners.
my fault, did not get what you were saying. as good a guess as any I suppose.
I think you and I view Surgebinding differently. I see the spren being attached to a point on the Spiritweb, just like a Hemalurgic spike is, except without requiring a physical spike. The spren can be gained but also be lost just like a spike, the effect isn't permanent so the spiritual aspect isn't actually made more powerful, just added on to, like a branch being grafted onto a tree.
It seems to me that how we view Surgebinding is just a matter of terminology. the spren adds her spiritual aspect to your own, increasing your connection to Honor as long as the bond exists. I'd say we meant the same thing after all, didn't we?
About the Pattern of Stormlight
Patterns of Stormlight filtered through the fabrial determine the power of the gem... The pattern cannot be seen with the naked eye.
Just as a reminder.
as Satsuoni pointed out, the fabrial is only the gem with a spren trapped inside. That's why I'd interprete that quote differently. A stone is cut in a special way. Light that enters the gem is broken in many many ways, the 'prismatic effect'. The cut thus creates a pattern of Stormlight inside the gem. That may or may not in addition interact with the spren trapped inside. All of this determines the power of the gem.
The only thing that we haven't really analyzed is what affect the holder of the gemstone has. They must have some function, or else they wouldn't be needed for Surgebinding, and Shallan's would have worked just fine after it was repaired. The only idea I've had is that perhaps the Shardblade damaged the spiritual aspect of the fabrial somehow. Another weird thing is that the Soulcasting fabrial doesn't appear to have spren trapped in it, just infused gems. The fabrials that need spren appear to be the ones that don't require humans to consciously use them. That's why I think the spren provide a Cognitive aspect to be used. They are primarily Spiritual entities but their power in that Realm would be enough to give them a limited aspect in the other two realms.It's also probably why most fabrials don't appear to be as strong as the abilities of regular Surgebinders. The fabrials only have small pieces of Honor inside them, but the Radiants had the Nahel spren so they had a much more powerful connection and a greater ability to use Surgebinding.
I believe the holder does not have any effect. As to Shallan's broken Soulcaster. So far, we have not seen any working Soulcasting-fabrial. Ok, we've seen only two anyway, one at least was a fake. I've sometimes considered the possibility that there is no such thing as a fabrial used to Soulcast. That ardents only fool everyone. That would mean that they are all Surgebinders. Which is not that odd to believe IMO, because they are scholars after all, following the Ideal 'Learned'. (understanding that Jasnah's order is #5)
Also, their Soulcasting-abilities are the only thing that gives them any importance. So it makes sense for them to hide the secret that anyone could learn to Soulcast.
And then, Soulcaster-fabrials are not fabrials in the modern way. Jasnah's surely looks like a real one, so uncut stones will be sufficient for Soulcasting. And uncut stones don't attract spren. So they are not fabrials. I'll come to your distcintion between old and modern fabrials, Satsuoni
Cut AND gem together determine the interference patterns, as well as the spren attracted and the resulting function.
Simply cutting a gem is not sufficient to make a fabrial, the spren must be captured inside somehow.
Possibility: the setting (wire around the gemstone) helps binding the spren inside. Break the setting and the spren may escape, leaving just a stone (a broken fabrial). The wires and connections also channel the power of fabrial (like the case of painknife, only the blades cause crippling pain, etc. An aside - I want a painsword in the hand of every lighteye soldier )
Good question: how can you capture a spren? Without physical aspect, it's difficult to conceive that. Again, I don't think the setting plays a role in this. The question is related to another: how is it that Stormlight is captured in gems? And this time it's also uncut stones, which will capture less Stormlight than cut ones.
I imagine it like there is mirrors on the insides of the gems which will reflect the Light. Normal glass always bends the Light and reflects some of it. Mirrors reflect much more. Remember that gems leak Stormlight and will grow dun over the weeks.
With cut stones we have much more surface to reflect the Light, so it captures more.
Spren are essentially Stormlight so it would work in a similar way for them. Only that it is captured definitively, perhaps due the additional cognitive aspect somehow.
Next is just my subtheory:
There are two kinds of fabrial - the old fabrials and the new fabrials. The old fabrials include Shardplate , soulcasters and possibly shardblades. These are powered by stormlight-infused gems, but not controlled by such gems. Their spren are either in the bindings /settings, transferred from the stones, or they do not have spren, and have instead a glyph circuits that channel the power from Stormlight, emulating spren. So if you cut the circuitry, either the spren escapes, or it is like trying to fix a broken microchip by gluing in together - won't work. (And yes, I see that Shardblade is very different, although it still has the gemstone, since it does not seem to be powered by stormlight at all. Maybe it already has it sealed inside without leakage, and feeds on the souls of those it killed )
And the new fabrials are the ones created by Navani - they are based on capturing spren in the gemstones, and then charging the gem. The gems cannot be swapped with another gems in this case, since the spren will be lost.
I oppose your idea of old fabrials
Concerning Soulcasters, see aboce. Shardplate and Shardblades are Invested objects, IMO. It has been confirmed for Shardblades:
Szeth's Shardblade would be mostly immune to Pushing and Pulling [allomantic], as it's an Invested object.
As Shardplate is also said to be given by the Almighty I say those are Invested objects as well. In my terminology, they are invested by a Primary Investiture (directly from Shard to object), as in opposition to filled metalminds for example which are invested by the human (Secondary Investiture).
I see no problem with Shardblades using Stormlight however. There is that gem on the hilt and it would be possible that the gem is infused every time the Blade is back in the spritual realm
Which is pretty often. Of course this is just a wild guess.
Why would Invested objects require Stormlight? It's similar to the phantom-army in Warbreaker. Those required Breath to hold together. They needed additional Breath to become 'alive'. So while Blade and Plate have magical abilities on their own, they still must be fueled.
This is a complete side note, but I just had the image of Kaladin going mildly berserk after Navani accidentally seals Syl in a fabrial, leaving him to break the stone and free Syl in what appears to be an either an act of insanity or a bizarre "spren rights movement" as applies to windspren in general.
On that point, we know that there are a range of sentient spren (from Brandon's Google+ Q&A), so I wonder exactly how magnetic the "attraction" of cut gems is to spren. Could Syl just say "Ooo shiny" and then fly away once she (as a thinking being) realizes the unnaturalness of her attraction, or would she be drawn in like a vacuum? It's a question of whether the spren's attraction to fabrials is as a moth to flame or as a filing to a lodestone.
There is also the question of whether a simple "windspren cut" would be sufficient to attract Syl, or if a specialized "Honorspren cut" would be necessary.
I really don't believe that Investiture-spren would get caught. Syl obviously would be intelligent enough to not get trapped. As to the others, I suppose they would be sentient enough too not get attracted as well. After all they are probably Splinters.
However you still have a point. How does the attraction function. Spren IMO are cognitive aspects without a physical body that have bound with spiritual energy (Stormligh or during Honor's splintering). I'd say that spren tend to want a physical part. so more like the moth to the flame.
If you've read everything, thank you for your attention and feel free to respond