You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
alternatehistory.com
One of the causes that caused Roman decline was unclear and not universally accepted succession, which allowed culture of usurpers to rise. The fact that some pulled it off only caused further usurpers to aim for the purple.
But would it be possible to have clear succession laws in place that would be accepted by all? Or would tradition of republic and anti-monarchical sentiments still be present even during empire and prevent it?