An Emperor and Kings

Say a country has twenty leaders who want to rule the country.  Only one can rule at a time.  As the current leader, would it be best to...

Eliminate all who aspire to be rulers
Allow your rule to expire so others may rule
Deny further rule until you have a successor
Imprison/restrict others who want to rule or reduce them to poverty
Allow them to rule as governors or subordinate leadership positions

If you choose the last option, how do you prevent them from turning on you or revolting? 

>>9

reading machiavelli isn't necessarily an answer to anything, particularly not this problem.
the world described by >>1 is too abstract for anyone to claim any sort of perfect solution.