Certainly, that would work the problem for Harry is that Molly becomes Queen. Mab in setting Molly as a Winter Lady candidate no doubt had this in mind, creating a massive disincentive for Harry to move against her and to protect her when vulnerable. Typical sneaky Mab.
That would need a real good argument to convince Harry. Molly could then have sex with Harry, so Molly may be up for it .
From what we saw in Peace Talks the only way to separate Molly from the Mantle may be to intervene before Molly become Lady in the first place, which means Harry has to Time travel back to Cold Days and save Lily, so Sarissa becomes the Winter Lady, but this would create a new timeline and not save Molly in the original timeline, only create a non-Winter Lady Molly alongside the Winter Ladt Molly in a different universe, Harry hasn’t save anyone.
Otherwise only perhaps Uriel has the power to reconstruct the original Molly, just before the Mantle because as a full intellectus he would have full knowledge of Molly mind, body and soul just before she received the Mantle and re-create her like a Star Trek Transporter rematerialising from an older pattern Even Mab, capable of teleportation seems only able to reconstruct things as they are, not as they were. In that scenario Harry removes the Mantle (I think he has figured out how to safely remove his, muting it by going past a threshold uninvited and then a summoning circle crossing the boundary, but the likely result an angry Mab slapping the Mantle back on him) and has Uriel bring Molly back to pre Cold Days. She would lose all the memories of being Winter Lady.
But as uriel often says he can do bugger all due to free will. The other side would need to do something huge for him to intervene to that extent.
