It is just me or you kind of underestimate Panacea/
I do think Panacea could undo Bonesaw’s work if it was all Bonesaw. The thing that made me think she couldn’t fix Grue was Mannequin’s parts. The casings, the technology, the pieces that aren’t covered by Panacea’s total control over biology.
Admittedly, those parts might’ve been fairly easily removable.