I don’t buy it. Stilicho had beaten Alaric several times and would have had the loyalty of the western army which was honorius’ biggest problem after Stilich’s judicial murder. I’m sure he would have thrown the Goths back. The question then is, could he have regained Gaul? My suspicion is that to the end he still hoped to use his old comrade Alaric to regain control in the West, as well as regain Illyria and its manpower resources but Alaric put the bill too high. Perhaps stilicho’s biggest mistake was his obsession with reuniting the empires? The right long term move but tactically wrong.