User blog comment:AltairKenwayAuditore/Assassin's Creed during the spanish conquest of america?/@comment-1845073-20120811073935/@comment-1888015-20120812180537

An Assassin wouldn't kill their target in the brutal fashion that Jack the Ripper does. They wouldn't be in the Order if that's how they treated human life.

So no, Jack wouldn't be an Assassin, and I wouldn't see him as primary antagonist material. At best, he would have a singleplayer mission to assassinate him, since his fate was unknown in reality, and he could be made into a MP persona due to the "psychopath" archetype.