Wow.. Just wow. Everytime i see these theories about Rey being Luke's daughter, I think "what a boring and lazy option that would be".
Like I said, the guy that played as Star Killer was in SW ep 7, but last I check no one is sure who or what he played as in this movie, and knowing JJ if he did play as Star Killer he was given a false credit to throw off anyone trying to figure out the plot for the new new trilogy.
That is some facetious reasoning.. The actor, Sam Witwer, is a Star Wars geek. He has voiced Palpatine and Darth Maul in the animated shows. Him having a cameo doesn't mean a thing. Unless, we apply a similar leap in "logic" and figure that James Bond is a stormtrooper because Daniel Craig had a cameo, or that Scotty had an accident and was deformed because Simon Pegg plays Unkar Plutt.