How would Syagrius' Domain of Soissons have evolved (politically, economically, culturally etc.) had it managed to get through the migration period ?
Here's a (not all that likely) starting point:
480. Julius Nepos discovers the plot by Ovida and the former western emperor turned bishop Glycerius (who was working for Odoacer) to murder him and flees Dalmatia for Constantinople.
481. Odoacer invades Dalmatia, defeats Ovida and appoints Glycerius as byshop of Milan.
482. Due to [insert reason here] Nepos fall out of favor in Constantinople and even hears of a plot (true or not) by Leo I to murder him. He takes his daughter, servants and money, borrows like crazy from everyone and then sets sail for the only place on earth he still thinks is loyal to him, northern Gaul.
483. Nepos, after a perilous journey, reaches Soissons in northern Gaul, then ruled by "dux" Syagrius (who was still issuing coins in Nepos' name). He dies shortly afterwards of unknown cause (old age, assassination, disease, you name it), but not before marrying his daughter off to Syagrius and naming him his successor and Emperor of Rome.
486. Using Nepos' money, Syagrius defeats the Franks, killing Clovis.
489. The Franks go south and invade the Alemanni starting a chain reaction. The Alemanni go south, pushing the Burgundians south-west, who in turn push the Visigoths out of southern Gaul.
493. The overstreched Franks loose to the Saxons and Frisians and then fragment into a couple of smaller kingdoms to the south. The Saxons migrate less to Britain given their new "Lebensraum" between the Rhine and the Somme.
Assuming the situation sort of stabilizes, how will this Roman remnant fare ? They have a largely intact infrastructure and are surrounded by small-ish kingdoms who are unlikely to crush them given skill and luck on the Roman side.
amateurishly made map:
