... If the apprentice was straight human it would be a pissing match with the WC because Harry isn't part of the wc anymore. And you know that the merlin would make it a "public" complaint to Mab ...
It's not like Harry's gonna "register" his new apprentice! The WC has already proven itself unable to track down newly emerging potential apprentices; how closely can they afford to watch Harry?
But then... Harry's still a mortal, and a wizard. Mab will ask, "Are you claiming, as the White Council of Wizards and signatories of the Unseelie Accords, that you have authority over my Winter Knight?"
Because ultimately, that's the claim the WC would be making: that they're in charge of what Harry does/doesn't do (that Harry
doesn't get to have/train an apprentice).
That claim isn't likely to carry much weight when Mab shows up wearing black.
... Maybe (thought I don't think it is) Thomas's sister has talent and can't sit on the sidelines even though she didn't turn. That's the kind of thing Jim likes to do to Harry. It would give Harry something to feel guilty about how Thomas will react if he ever gets him back
Ooooh, Inari! That's another interesting option!
I like it, indeed.
I still think Fitz fits better. We
know he has some level of magic. I like Harry looping back to him, to give him a bit of testing & training... but eventually passing him off to Morty as the better teacher for Fitz's talents (and this giving him the idea of leveraging the Paranet (and the array of minor talents & sheer number of clued-in observers therein) in an organized fashion to find/train new & emergent talents & prevent them from turning warlock).