Could Justinian have decided that reconquering the old province of Dacia and exerting Roman authority to the Carpathians (everyone's favorite hypothetical Roman border) was worthwhile?
It would have the avantage of being closer to the capital, and there's decent rivers for logistica. And holding the area would make Thracia more secure.
On the other hand, its more exposed, and the Avars are just about to arrive on the scene, and its poorer than Italy or North Africa.
As a tangental advantage, if this invasion is prior to/in place of the invasion of Italy, it could encourage the Lombards to invade Italy early, and weaken the Ostrogoths.