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I would have to say Yana would work well with Pietro and Penny. I could imagine Pietro wanting to help Yana with the drums in his head, but can't find anything wrong with him. As for the Utopia project, Yana would work on Amity instead.
I don't think they would open the fob watch, as Yana said it was broken (even though he was found with it). I could see Pietro and Penny taking his word for it. The only reason Yana opened it was because Martha freaked out about it.
If someone did open it, I'm not sure what would happen. I mean, would the Master's life/memories transfer to that person? Or do they go to Yana? I'm really not sure. If the latter is the case, he might work with and betray Salem. He might try to steal her immortality so he won't need to regenerate.