I do not doubt Mab has plans for Thomas, but having him in stasis is part of those plans, which means she knew about or predicted the Thomas situation but did not engineer it. Mab is spectacular at taking advantage of somebody else’s decisions to their detriment. Ask Nicky.
My guess is she put manoeuvred Marcone into hosting the Peace Talks, knowing full well the likely participants who would attend ( I think only River was unanticipated due to Harry’s intervention) white Court, Swartalves, White Council and who would be there for the White Court, Eb. She knew both Harry’s and Thomas’s living arrangements and knew of Eb’s views on Whamps and Swartalves, she just needed Eb to visit Harry at home when Thomas was there. It would indicate that Mab is ultimately behind the push to oust Harry as that is the urgent reason Eb had to visit Harry (Carlos didn’t raise it). Everything else on the Thomas incident arises from that. Thomas creates the excuse for Harry to go to Demonreach. Without the Thomas incident Harry would have been drafted by Eb and not made it to Demonreach. One of the first things, Eb does after Ethnui’s ultimatum ask where Harry is before it is even known Thomas is gone.
Mab works for more than one reason, she needed Harry of his own free will to go to Demonreach to pick up the weapons, despite being under favour to Lara and she needs to later on discredit Eb for some reason. If Eb is becoming unstable he needs to be relieved of the Blackstaff by the senior council, in circumstances where Harry will be awarded it by the Senior Council.
If the Blackstaff is Mother Winters walking Stick it can be returned to her, or it can be bestowed on another Wizard, she may intend Harry to take it to make him more her Knight, but I think he would reject it, he’s seen the effect on Eb and realises it would make it much easier for him to become a monster. He may instead return it to Mother Winter outplaying Mab and earning him a favour from her totally stymying Mab because if she ascends to being the Mother might herself have to repay that favour to Harry.
Mab may finally have outsmarted herself, which would gibe with Christmas Eve, she appears very contrite in paying funeral expenses/medical bills, and in providing a gift for Maggie. Very unlike her But does not appear herself, sending Molly. Harry finally has something over Mab, rather than the other way round. A favour from Mother Winter would do it.
Setting aside the Black Staff , which would allow Harry to kill Marcone without consequence would show Marcone that Harry will not kill him in cold blood ever. That may affect the disposition of the BFS building. Marcone is very dismissive of the “so-called” White Council in Even Hand.
By making it clear to the White Council that the Laws of Magic apply to all Harry would be seeking rescue their reputation. No more executions, No more black ops breaking the Laws.
Perhaps Harry will not be the Winter Knight Mab wants, but he may end up being the Winter Knight Mother Winter wants, a check on Mab. Mab won’t have been allowed to know what went on between Harry and the Mothers, the one person who could out Mab Mab is Mother Winter, with Harry intervention.
