One particular person would be rather difficult, unless it were someone as prominent as an Augustus, and even then there is already a lot of stuff on him and others. Maybe do an aspect of the period? Provincial Corruption under the Principate could examine how, if at all, the new imperial administration affected provincial governance. Political Gestures under the Early Emperors could look into the language, scope, source and direction of political appeals, senatorial decrees and other such 'public relations stunts' (?) and how they were changed under Augustus and his successors when compared to the first century BCE. You could even do a group of people: Freemen of Rome, 44 BCE-17 CE or Equestrian Rights under X. The point of the dissertation is to be creative!