Rome and China have a lot of similarites. Both have similar climates, both were threatned by barbarians from the north, etc. However, there is one big difference between them, and that is that China and it's culture have survived throught the millennia while Rome and it's culture have not. So I would like to ask: How can I make Rome survive like China did in OTL? I would like Rome to survive with the culture, language, etc. it had around the time of Christ, just like China. And I have one requirement: This surviving Rome must control the Italian peninsula and the City of Rome, so no surviving Byzantium scenarios unless Byzantium contains Italy and Rome.
This is just a very quick write-up.
Easy. Eutharic, or rather Flavius Eutharicus Cillica, does not die in 522. Theodoric's plans for establishing not only a strong Gothic dynasty ruling both Spain and Italy are not foiled. His relations with the Senate and Roman aristocracy do not sour like it does IOTL. Theodoric the Great dies more or less at the same time, succeeded by Eutharic. His relationship with the Roman emperor Justin I sour due to the latter's anti-Arian persecutions but he manages to convince him to grant Roman citizenship to his wife
Amalasuintha and children Athalaric and Matasuntha. Flavius Eutharicus has a strong friendship with Cassiodorus, nominating him to the consulship on numerous occasion, and making sure that he remains on the Senate's good side. Eutharic's presence assuages the Gothic nobles who IOTL pressured Amalasuntha to raise the young prince Athalaric as they saw fit, pushing him to drink heavily; instead Athalaric's education is balanced equally between the Goths and Romans.
Eutharic maintains the rocky but manageable relationship with Justin's successor Justinian. He sends several Gothic warships and troops under the command of Flavius Theodahatus, with the teenage prince Athalaric tagging along. At the battle of Ad Decimum, Athalaric commands several hundred Hunnic mercenaries and defeated a detachment of Vandalic horsemen led by Gibamundus. He receives kudos from the Roman general Flavius Belisarius and sparks up a friendship. The Vandalic War more or less ends the same way. The Goths receive little in turn except revenge on the Vandals and imposing a hegemonic influence over the kingdom of Sardinia, ruled by Godas. The remainder of Athalaric's reign is spent reforming the Gothic army into something that could match the Eastern Romans in a possible war. No such war happens, at least not during his lifespan. The reformed Gothic army is sent against the Suebi and Franks, bringing them into heel. Eutharic passes on in the early 560s, elevating Athalaric. Unlike Eutharic and Theodoric, Athalaric has no such allegiance towards Constantinople. He orchestrates a civil war against IOTL Justin II and Justin, son of Germanus. He also sends emissaries to Ctesiphon and convinces the Persians to declare war against the Byzantines. Amidst all this chaos, Athalaric not only declares himself Augustus of a newly reformed western Roman Empire, but decides to support the son of Germanus, offering him the hand of Matasuntha. The pro-Ostrogothic Justin wins out against the IOTL Justin II, becoming Justin III. Justin III reluctantly accepts Athalaric as his equal in exchange for western assistance against the Persians. The Persians are eventually defeated (for a time) and there is a military triumph, celebrating the glories of emperor Justin and Athalaricus.
Rome is restored, in both west and east.