I always assumed his teammates sort of looked past Pietro's attitude. They know he says mean things, but means well most of the time.
I agree that neither Emma or Psylocke are good matches. I'm just throwing it out there If Pietro finds out how gung-ho Emma was about killing Wanda during House of M, that will torpedo any likelihood of them even being remotely friendly with each other. Although their bitchy personalities would make a relationship kinda funny.
Jean Grey would be the best telepathic girlfriend for him, and given she's young now, it would make the relationship very wrong ....and yet, the more I think about it, the more I want to see it happen out of sick curiosity. What would Cyclops think? OR they could bring young "Brotherhood of Evil Mutants" Quicksilver to the present, and he hooks up with Jean Grey!