Kemp,
Poor example? If liberalism and autocracy are a contradiction, then no autocrat can rule liberally. To prove you wrong, I only need to provide one example of a liberal autocrat. Insisting that succession is essential to the definition of liberal autocracy is misguided. With that logic, we would have to apply it to democratic governments as well. Plenty of liberal democracies evolved in to illiberal ones. Likewise, the United States is becoming more illiberal. So if succession is essential to the definition of liberal government, then liberalism and government are a contradiction. Additionally, your reasoning about the illiberal evolution of autocracy applies to democracy as well. So we would have to say that every government inherently heads towards an illiberal direction. At best, it takes longer for a democracy to become illiberal.
Since you don't like those emperors, then I'll provide a stronger example, Augustus. Augustus generally respected the rule of law, invested in public goods, was tactful with the senate, and enacted free-market reforms to stimulate the economy. He maintained these free-market policies for the entirety of ~40 year rule.
Augustan Economics: http://www.cato.org/pubs/journal/cjv14n2-7.html
Augustan Rule of Law:
"Opposites do not have to be mutually exclusive, and we are not obliged to choose one or the other. The story of his career shows that Augustus was indeed ruthless, cruel, and ambitious for himself. This was only in part a personal trait, for upper-class Romans were educated to compete with one another and to excel. However, he combined an overriding concern for his personal interests with a deep-seated patriotism, based on a nostalgia of Rome's antique virtues. In his capacity as princeps, selfishness and selflessness coexisted in his mind. While fighting for dominance, he paid little attention to legality or to the normal civilities of political life. He was devious, untrustworthy, and bloodthirsty. But once he had established his authority, he governed efficiently and justly, generally allowed freedom of speech, and promoted the rule of law. He was immensely hardworking and tried as hard as any democratic parliamentarian to treat his senatorial colleagues with respect and sensitivity. He suffered from no delusions of grandeur."
-Anthony Everitt, British academic