So as of the current rules, a TO would be able to DQ someone if they show up with a Scum Squad.
Technically you may be correct, if you wanted to argue purely RAW then there's some merit to that, the rules do say you have to field either a rebel or imperial list.
But it also says that all products are legal once released, and there was an email from FFG that I can't find now that said TO's can't actually refuse to let someone use S&V ships once they've been released.
Undoubtedly they'll update the tournament doc and FAQ about the same time that S&V is released.
To be on the safe side, one could bring a Rebel/Imperial squad as backup if the ill-informed TO tries to DQ them.