What attracts you to Late Rome?

[Flavivs Aetivs]

Illyricum would have been a problem, true, but without the sharp rivalry, even the state of war between East and West, it would have been far less a problem. Without the threathening attempts by Stilicho to gain superiority in the East, Constantinople would have been far more inclined to let Illyricum go back to the West. Or split it up, as happened. Rome also recruited a lot in Gaul, which became a problem when the infrastructure became disrupted by the invasions of 406 and afterwards. With a more stable Rhine border, Gallic recruits would have been more available.

Illyricum was divided up pretty much in a straight line south of sirmium.

Also, Aetius managed to achieve a stable Rhine border several times by pushing the franks back past Colonia and Trier.

But in reality, I don't think there was any hope for the west. The Romans were unable to create an effective model of government, and without a law passed for succession rights (although there was an implied gavelkind succession) the empire would have still fallen. There was nobody to replace Aetius after he was killed, except either his son Gaudentius or Majoran. But the former was kidnapped in the Sack of Rome and the latter came to power under Ricimer only, so although he was effective he was still a puppet and he came to power after the death knell had been rung.

Without stability and some way to motivate new recruits, along with a reformed economic system (rome was horribly oppressive and somewhat socialist) collapse was inevitable.