The Sovereign

This seems unlikely since "Ala" is the Aon for Beauty/Handsomeness. Presumably the Skaze would be named whatever Fjordell character is at their core, not after an Aon.

I added a couple of questions that came up during my re-read of "The Lost Metal".

Not to trample on your idea, but I suspect it would be impossible to accidently reassemble a Shard essentially regardless of the tools available/circumstances. The process would require Intent.

Autonomy may be interfering on Roshar via Sja-Anat.

I think it is safe to assume with Shallan Re-Swearing Oaths Testament is more alive than other Deadspren.

I suspect you are on the right track, but not all the way the way there. If the drawing were colored, I'd guess the gray would be Red. I don't think it is a matter of them trending toward choosing to allow Sja-Anat to Corrupt/Enlighten them, I suspect the Oathgate Spren depicted as Grey are already Corrupted/Enlightened. The Oathgate Spren are Manifested Ink Spren which I'm increasingly convinced are the embodiment of the concept of the written word. The limited dialogue we have from Ivory and Blended shows that they view the world as a whole in a dichotomy of Is/Is Not. This makes a lot of sense as I'm pretty sure the Black/White aesthetic is a physical depiction of Fact/Fiction. The "Freedom" the Inkspren refers to may be the ability to see the world in the "Maybe" so to speak after being Corrupted/Enlightened.

Just a thought; The Oathgates are likely a pair of Manifested Ink Spren. One is present in Shadesmar while the other is Manifested in the Physical Realm. When the Oathgate changes realms they switch places. Presumably the black guardian is the one currently present in Shadesmar and the white guardian is the reflection of the one Manifested in the Physical Realm. Something of a tangent, but I assume the Ink Spren are the embodiment of the concept of the written word which explains the dichotomy of their speech; Fact/Fiction. I completely agree with your assessment on why Sja-Anat hasn't Enlightened/Corrupted them.

I added a question about SA. This one is more of a "theory" than a question; This seems intuitively obvious to me. From a story telling and pattern perspective it makes sense; As we know, Ash and Taln will be POV characters in the back 5. 10 Orders, 10 Flashback Characters; Dustbringers and Stonewards are the left out orders of the Protagonists. Taln will obviously be the Stoneward which leaves Dustbringer to Ash. I suspect the Oathpact will be completely dissolved by the end of SA5 leaving Ash and Taln as "free agents" while Ash is the Patron of the Lightweavers, her maddened state is far more in line with the Dustbringers. Also during Oathbringer Dalinar and the Stormfather comment on who "Two are missing" from their Radiant circle.

It seems more likely to me that Mercy put Ambition out of her misery (a "Mercy killing" so to speak) after she was severely (possibly mortally) wounded in her fight with Odium rather than actively helping Odium in the conflict.

Something to consider; Mr.T's Boon/Curse affects more than his intelligence, it also makes him inversely passionate and logical. Assuming this is intact as Odium, I would guess that on his passionate days the Power would be in greater control and on his logical days The Vessel would be in greater control. This would have the further implication of limiting or unchaining his ability to act as Odium. While highly Passionate he will be more in line with the Intent of Odium and likely would be able to act freely. When he is logical he would be working against his Intent which could cause him to have trouble acting.

Widor or very least Zigareth; Wyrn's palace in Widor seems plausible to be a Fabrial city. Silverlight likely is as well. Presumably Widor; Zigareth would amplify uses of the Dor via Dakhor. I would guess it would amplify how much output you get from a sacrifice. As Silverlight is a melting pot of people from all over the Cosmere, the possibilities are numerous. A sidenote regarding Elantris, we have a few WoBs about this:

@alder24 Thank you very much, that was a very helpful response! I used to be very up to date on the WoBs, but fell off the wagon a couple of years ago. I have been working my way through all of them from the beginning and doing my best to search through Arcanum before adding new questions, but there are definitely some gaps that were not answered at the time I had originally added the question or that I simply forgot, missed, or haven't got to yet. Regarding "TherehastobeananswerWhatistheanswerStopTheParshendiOneofthemYestheyarethemissingpiecePushfortheAlethitodestroythemoutrightbeforethisoneobtainstheirpowerItwillformabridge" the "ItWillFormABridge" is what indicated to me that it may be talking about Rlain; Tumi calls him "Bridger of Minds".

I just added 2 more Stormlight Questions and a Mistborn Question.

With Chapter 5 & 6's epigraphs I think I'm at least partially right. Though the page 4 quote makes me think the author could also be also be Jasnah. Another thing to consider is the Spren, it is possible that Kal or Szeth die (Szeth seems more likely) so the below mentioned Witnesses could be one or the other and their Spren (If this is the case Kal and Syl would be my guess).