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What do you think would be the final POD to keep the WRE survive, even as a rump state, at least until Justinian reconquest?
I think the latest one would be a Western victory in Frigidus with the majority of the Eastern losses falling into the Goth. By the time of Majorian, it was far too late.
An even stricter late POD would be Gratian remaining independent of Ambrose, and remaining sane (not doing things like taking into his personal service a body of Alans, and appearing in public in the dress of a Scythian warrior, which directly angered the legions and caused the Maximus rebellion).