Well, for an Elantrian losing the devotion, I don't think that matters much. The Hoed definately didn't have devotion anymore, and they didn't become un-shaod-ified. And I doubt the entire fully realised Elantrian society stayed constantly devoted. The Shaod is, I feel, more like a pat on the back from the remnants of Devotion saying "Hey! Thanks for upholding my intent and stuff. Here you go."
And for the Nahel Bond, I would imagine that without the personality shift like you suggested, yes, the spren would die. I think the big question here is if the spren could actually be tricked well enough to choose a person under a rioter's influence. A crazy combo-thought to consider is what if a forger teamed up with a rioter? The rioter flares the metal, makes Honor the key trait, and the forger prepares a stamp that essentially writes a history for that person where that Honor was natural. I wonder if that would stick at all.
And that makes me think of a forger's use for Sellish magic on a foreigner. Would it be that big of a stretch to stamp someone to adjust the place they were born in their history? Forging is one of those magics I don't understand very well, and I need to go back and reread the book, but I don't think it would be that hard of a stamp compared to rewriting one from scratch. Especially if you had the cooperation of the person you were stamping to fill out details and such.