... And Bonea would know at least some of that Angelic magic. Also Bonea would know what it means to be a Starborn, since we know that Lash did...
I don't think we know that Bonea knows everything Lash knew, let alone everything Lasciel knew.
In fact, I'm pretty sure the human brain (which is the material Lash had to work with) isn't CAPABLE of knowing everything an Angel knows, so Lasciel's Shadow didn't (
couldn't!) know everything Lasciel knew. I wouldn't want to estimate it as a percentage or fraction, but I suspect that shadows have VASTLY less info than their Fallen, a tiny fraction rather than a substantive part.
Also, I suspect that the Fallen can probably CHOOSE what info to imprint into a given Shadow -- THIS one will know more about combat and other direct sorts of conflict; THAT one will know more about social stuff and "soft power;" etc). I presume the Shadow given to Dresden was stuffed with esoteric knowledge, magical secrets, etc... y'know, the stuff to best tempt Harry with
.
I expect that Bonea has some subset of Lash's information, what Lash was able to arrange
in extremis, in the scant moments available.
I presume Lash was prioritizing what would be most useful to Harry (Lash has a very hard-nosed & practical sense of "useful"), agonizing over what would survive
where within his mind, which things she'd leave out, which pieces she would buttress and protect, what would likely be blasted to uselessness... desperately working to give Harry the best odds she could, in the moments before the blast arrived. Very cinematic/heroic/tragic stuff!
She died doing the right thing.
Plus, that limited-info gives Jim the excuse he needs to have Bonea
not be the
Deus Ex Spiritus solution.
It remains to be seen what she knows, of course... which details are / aren't preserved... whether everything is "on tap" for immediate disclosure... whether there are layers hidden away (like BlueEye Bob inside OrangeEye Bob)... maybe even Lash herself? ... etc ...
... Top that with the fact that Lasciel(the fallen) is trapped in Hades domain with no shadow to summon her back. Unless some of your theory comes to pass.
Remember how Nic came through
after everyone else? FAST.
Nic got Lasciel's coin from the vault, and he got Ursiel's from the icefield; that's WHY he was so late at the gate (we already know he could move really, really fast).
Not even gonna call this'un a "WAG," I think it's so much an odds-on likelihood as to approach certainty. We already have WoJ that Lasciel is making another appearance... and Lash too, iirc.