With Iron Man, they just changed the origins of his suit from Vietnam to Afghanistan. But what subsequent historical event is likely to have the same gut-punch factor as the Holocaust or to have such an obvious impact on a character?
I think all they can do is make Erik the child of Holocaust survivors, who has had the importance of it drilled into him so much that he may as well have lived through it himself.
The Holocaust is obviously history's most infamous crime, and may it ever remain so, but there were plenty of other atrocities in the rest of the 20th century, and I find your implication that the children of Holocaust survivors born after the fact could be dramatically more psychologically scarred as
actual survivors of warfare very troubling.
Heck, there could be a Vietnamese Magneto, born and raised in My Lai.