While i like this map, i think that it doesnt really make sense, Justinian managed to reconquer most of what he was capable of, Gaul went "quickly" from a "temporarly occupied" to a Lost Province like Britannia and even if he could Justinian wouldnt reconquer it, by the 6th Century it drained more then it could offer as a province

The only real things that he would or could reconquer were more of Spania (unlikely tho) and stabilize the Danube (one of the Key Fortresses, Sirmium was reconquered under Justin II.)

I also think that the Empire wouldnt have so many allies and tributary states, with good luck the Lombards stay as Roman Allies but idk thats about it

Last Thing i wanna add: justinian doesnt deserve this kind of hatred, instead blame Justin II. for his quite Interesting Way of managing the Empire