I'm intrigued. What happens if Zeno or Anastasius have a moment of Theodosian foresight and realise that the only way the Roman Empire can be saved from disintegration in the West is by proclaiming Theoderic Western Roman Emperor and thus giving the Goths a stake in the preservation of the Empire? Would the war-weary Roman nobility really go to civil war over this?
The idea is interesting but it would take a very different Roman Empire than the one that existed during the reign of Anastasius and Zeno.
Zeno had a too weak grip on power and it took him all of his reign to reinforce the Eastern Empire and even then he was forced to fight several revolts during his reign. Despite being a descent of a family that had lived for five centuries as Roman citizens the fact that he had been born on a tribe from the borderlands made his own citizens see him as an upstart barbarian, the only thing that worked on his favor was that he followed the "right kind" of Christianity instead of the Arian believes that the Germans preferred.
If Zeno, that was considered an upstart half barbarian, dared to declare that Theoderic was the new Augustus of the West and his equal, for if he declares him as Emperor then he declares that he, Zeno, and Theoderic are equals, then expect massive uprisings and several revolts.
Anastasius managed to be decently loved by the people, was recognized as a true Roman (he had been born in Illyria and this played in his favor given that many Emperors came from the Illyrian provinces) but was a Miaphysite and this created him problems with the cleric, especially because he ruled during the Acacian schism.
While his reign was more smooth than Zeno's he also couldn't make Theoderic an Emperor without massive problems.
First Theoderic was an Arian, Anastasius an Miaphysite and most Romans were Christians. If he declared Theoderic, Augustus and Imperator, expect massive religious uprisings and the Acacian schism could get even worst than it was.
The same problems that Zeno would had also apply to Anastasius.
To get past this problems the Roman sense of superiority as to disappear and that needs a POD during the Republic.
Historically the new kingdoms that formed in the lands of the former Western Empire had always two systems, one that applied to the new peoples and another one that applied to the "Romans".
Law codes usually were divided in two, one to the Goths and another to the Romans.
Both sides were usually encourage to stay apart from each other, given that neither consider the other an equal. The Romans, despite all, liked to see themselves as the ones on the top a marble column while they looked down on the "barbarians". The Goths, while they admired the Roman culture and civilization, they thought them as weak and soft.
The "I'm your viceroy but don't even attempt to give me orders" was the best both sides could accept.
The Romans were, theoretically, above the Goths (Theoderic was "officially" a vassal of Constantinople). In contrast the Goths left the Romans at peace and in exchange for protection all they demanded was taxes.
Extra: If they declare Theoderic Emperor, he might not accept the title. Being the Augustus of the West would put him on the wrong end of the Franks and of the Visigoths given that if he accepts the title he is declaring that the lands the others control are his, because those lands were part of the Western Empire, and this could cause war between them.