Thank you for all the quotes you provided here!
The body switch made Luccio more susceptible to the ink than a wizard of her age should be.
A few quotes from the book (all are from the paperback version and all italics are my emohasis)...
From pages 128 to 129:
from pages 518 to 519
from pages 526 to 527
Luccio is older than Morgan and Eb said in the first quote that Morgan could not have been forced to kill against his will. Luccio was more susceptible because of the body switch and the resulting younger mind. Peabody was able to have a greater influence on her with his ink...
And yet, none of those quotes (nor anything else I recall Ebenezer ever addressing directly) actually states that the bodyswap made Luccio more susceptible to the influence of the inks, and to Peabody's magic.
We infer it, from the 1-2-punch of Morgan telling us of Luccio's guilt and from Ebenezer says.
... I doubt that Peabody could force an older wizard, including the Senior Council, to accompany him to the island. That goes far beyond the nudging Eb mentioned. If a Senior Council member was present on the island, I believe they had to be there of there own will as a co-conspirator, not because they were forced to by Peabody. Both Eb and Harry believe that it was Cristos on the island with Peabody, but we know that they could be wrong.
So, here's some other thoughts; alternative hypotheses.
#1 - Ebenezer is just wrong. We know that the Council has largely forbidden the exploration of mind-magic, but Peabody & his ilk clearly have not. Corpsetaker had remarked on how out-of-date Harry's training was, and I think we should take it for granted that Eb gave the best mental-defense training that he could, to his grandson. But what if Black Council researchers had found ways to bend even Senior-Council level minds, without breaking them?
#2 - Luccio is Black Council. This is a dark theory, but -- what if Luccio killed LaFortier not because of Peabody's mind-control, but because she's a full-on BC agent? What if "Peabody made me do it" is just her cover-story? Consider this: of
all the people in Edinburgh who could have discovered her... who's the
one person who would cover for her, take the fall, but
also have the skills & power to escape the WC, and the initiative to loop-in Dresden? How "convenient" for her, that that one person was the one who found her there with the bloody dagger.
#3 - An overt, brutal, full-control takeover may not be possible, or may be prohibitive. But repeated nudges, year after year? That exactly what sets habits and patterns in place, which can become self-sustaining: "You are what you do." Small incremental changes, that are let to sit and "naturalize" in place... which in turn can form a new baseline, from which you make further incremental changes, set new habits and patterns.
And it's not like the Council was a bastion of loving-kindness, trust, and openness; there were innumerable doubts and grudges and suspicions to exploit, bad inclinations that pre-existed, that didn't so much need a "nudge" to be go badly, as just gently suppressing the inhibitions that might have stopped that bad decision.
How many
years was Peabody inking the Council?