WI: Justinian II held onto The areas of North Africa that he conquered

  Well if he had avoided some of his mistakes, such as not supporting Belisarius earlier which might have enabled the quicker conquest of Italy without the long devastation that resulted he would have a better chance although the devastating plague strained the empire.  This and half-way decent leadership following from him might have meant that the later Lombard invasions could have been defeated. 

  I'm not sure the small footholds in Iberia could have been held indefinitely, although the Visigoth empire was faltering.  However while religious differences would have continued to be an issue holding the N African coastline regions would have been a step forward.  Enabling it to recover from the chaos following the fall of the western empire.  It would have made the Med in general safer for merchant shipping and trade, although of course the big disaster here was the loss of both eastern and western N Africa to the Muslim conquests which completed the destruction of the economic system that had existed during Rome's peak periods.

  Duh sorry. Your correct.    Justinian I gets so  much attention I just didn't look closely enough.

  There was an interesting TL on Justinian II on the AH site - talking about 10-15 years back before I left it - where he hard a near death experience in traveling back to Constantinople after being overthrown and exiled and then regaining the throne - which made him somewhat less paranoid and bloody and it was looking quite interesting.  Think it was being written by Sargon IIRC. 

  I must admit its so long ago I can't remember much about him.  Checking his wiki entry it doesn't mention any successes in Africa but some early successes against the Caliphate although later reversed due to his erratic and unpopular policies.  Carthage itself was lost to the Muslims in 698 and the city largely destroyed to prevent it being reconquered by the empire.

  There are options, with a different personality, especially in his 1st period of rule.  If he makes less enemies and is somewhat less extravagant he could break the power of the landowners with the support of the ordinary people and get the economy in a better state.  Also keep the peace with the Caliphate until he has really secured the Balkans, plus making sure he can rely on Slavic forces elsewhere. 

  Africa would be a factor and holding onto and expanding the territory around Carthage would be very useful but I think actually the Balkans and Anatolia are more important to the empire, at least for a decade or so.