Great post! I agree on your point about Veil having attributes of Shallan. I've been re-reading OB and I'm beginning to toy with the idea that the "masks", by the end of the book at least, are extensions of Shallan. You mentioned the theft and spying part of her, as well as her feelings for Kaladin, being put on Veil.
To add onto that, I think the parts of her that were able to kill Tyn, and her parents, basically the "soldier" in her, have been pushed onto Radiant. I also think the traditional and religious part of her have been pushed onto Radiant as well. I noticed in WoR and WoK, Shallan was religious, or at least more religious than the average Alethi. Some examples were the prayer to herself when Jasnah was speaking of the Almighty being dead, and the ones she did after people died at the camps she met Vatath, but on her Wedding day, it was only Radiant that was concerned about her doing a prayer before her Wedding, and she eventually doesn't do it. Which I think add on to the point of her being fractured by the end OB and the "Shallan" that has married Adolin isn't the complete version of her.