I would like Emma Frost to appear, if only for it to flow thematically. Would be kinda weird how the last scene of FC is Magneto rescuing her and taking her into his gang, and then in the sequel she's not even in it.
I also wouldn't mind more Moira, if only because Rose Byrne is so damn beautiful.
This is going to be epic. I'm still hoping for my "Order 66 montage" idea where we see the Sentinels kill loads of our beloved X-Men
And imagine if all the Marvel universe were under one movie roof, as in the comic you could include all the big superheroes being iced by the Sentinels- Spidey, Iron Man, Cap, Daredevil, Ghost Rider, etc