What if, after accepting the terms of Pope Leo ("you can take Rome's wealth, but leave its people"), the Vandal king Geiseric doesn't loot Rome...
...what if, instead, he has himself* made Emperor of the Western Roman Empire?
(and appointing his generals to prominent places in the government, to keep them from simply looting when they arrive in Rome)
thoughts?
* = or his son, already promised to marry the Princess Eudoxia.