I always wondered on the other side if the 'Low Empire' days couldn't have had some reforms on the political, economical, and army sides ongoing to help the West side at least to survive and fare actually better. Even if it means ending this tradition, culture and nation into a new 'créole' way.
Political reform: Restore the Republican system with better checks and balances or at least codify into Roman law the Five Good Emperors succession system with Senate oversight, which will actually lead in the long run with a federalization of the Roman Empire and inevitable cultural and social consequences of such federalization, which would be more like practical Balkanization.
Some form of medievalization will also happen by the time the Huns invaded Rome since the Danubian provinces will be more militarized and will probably go together in making a slow expansion into Germania. If the barbarian Germanics will be halted at the border, they might just be contented in settling down alongside the borders as what happened in OTL in a smaller scale which will lead to the formation of Roman client kingdoms in Germania.
I still see Christianity to be around, and most likely, will not morph into the Roman Catholic Church and more or less discriminated by most of pagan Roman society but not much persecuted anymore; especially if closet Christians started to sprout out in high ranks of Roman society and start the forces of religious toleration or even Enlightenment concepts of the separation of religion and state.
Rome will be stagnant territorially though, or it could expand territorially but will not necessarily mean an expansion of administrative forces from the political center into the newly annexed areas, since administration is already heavily decentralized in most parts of the long held areas.
Administrative Balkanization will happen in Diocletian like structural manner but even more fragmented, "Civil Wars" will be common in a way that the entire Roman sphere is practically Holy Roman like and it is just like OTL's European wars and most likely concentrated in less populous and prosperous Western territories and NO INDUSTRIALIZATION, HERO OF ALEXANDRIA LIKE. A form of proto industrialization might happen but that's it, at least for a VERY LONG time.
"Romans" will get to the New World, have more contacts with China and India but the Roman New World colonies would be like a collection of separate countries, practically independent.
The Butterflies Are Staggering.