I don't know if the X-Men have the rights to use Quicksilver and The Scarlett Witch. They debuted in the X-Men comics but the bulk of their time has been spent with the Avengers and I would assume Marvel Studios owns the rights to them.
Hasn't Lorna Dane being his daughter been retconned a bunch of times? That being said, I'd like to see her as a new character in First Class 2. It would give both the X-Men (especially Havok) and Magneto a personal stake and would explore the Magneto family man concept.
You know, they did change the nature of Hank's mutation in the sense that he had big hands as well as big feet. He could definitely hide his feet in public so I didn't quite get all of his complaining about his mutation. Although I can definitely see that being a problem with any potential love interest.