The Roman Empire of OTL is generally considered to have passed through two phases: the Principate and the Dominate.
The former was (with a few exceptions) marked by a system of cooperation between the emperor and the senatorial elites. The emperor was mostly relegeated to military duties, and the empire was kind of informally divided between imperial and senatorial provinces.
The latter, meanwhile, was more absolutist in nature. The emperor's duties began to encompass not only the leadership of the armies, but also control over practically every aspect of political, bureaucratic, and religious life. The senate had its influence heavily curtailed, to be overshadowed by the consistorium of the emperor.
The period of transition between both "phases" tends to not have a defined consensus, with most putting the beginning of the Dominate to during or after the Third Century Crisis, others putting it all the way back to Septimius Severus' reign, etc.
So, my question is: had the Roman Empire not suffered its "midlife crisis" (reign of Commodus, Year of The Five Emperors, Rise of the Sassanian Empire and Germanic barbarians, Third Century Crisis), do you believe the old structures that defined the Principate (emperor-senate cooperation, traditional Roman-Hellenistic religious systems, etc.) could have survived?
Or are you more skeptical, and believe the empire was getting too cumbersome to not be governed in a centralized, autocratic manner?