I feel like there could be something interesting with Jean and how you describe her as split between mind and heart. Pietro would accept either without seeing any real dichotomy or anything worth commenting on or being surprised by (it's probably hard to surprise Pietro anyway), and at his best, he could keep up with her on the mind side, if she wanted to analyze, he could be right there with her... I'd be interested in a dynamic where maybe he ended up feeling challenged to use his powers better?
Irene...if they did spend much time together, it sounds like it'd be a bit of a dance of chameleon and mirror kind of thing, neither of them quite finding what they're looking for? (Pietro wants to fit in, not be analyzed, Irene wants to either do what's needed or get what she wants, things endlessly shift around as they react to each other?) Either that or by this time they're totally comfortable with each other, having danced their way to some equilibrium? I doubt Pietro is/was very receptive to the psychiatrist aspect, though, but then, he's just a hanger-on at this point. Probably thinks it's good that she's taking care of Wanda some of the time, and then encourages Wanda to do dysfunctional stuff the rest of the time...
And yeah, Tabby would likely not have a hard time persuading Pietro to be wild with her, if she wanted.
Oh, and if you'd like to play something with Wanda and Pietro, let me know :)