I've been reading Edward Luttwak's, "The Grand Strategy of the Roman Empire," and it's gotten me thinking about possible ways to reform the Roman army during the early empire in ways that will mitigate the perennial civil wars that plagued the empire for its entire existence. It's difficult to do without an insane degree of historical hindsight, which obviously any characters in an ATL will not have, so how can the leaders of the Roman Empire plausibly establish institutions that will mitigate either the causes or effects of the civil wars? Bonus points if it's a solution that wasn't eventually settled on IOTL.
To reiterate, the goals are:
--fewer civil wars
--mitigation of frontier weaknesses when civil wars do eventually break out
--a more secure, legitimate central government
--no 3rd century crisis