I'm not sure that Gregorius Turonensis could write about this events. He wrote about first invasion of Franks to Italy, yes, but not about Maurice's plans. He died erlier (591AD) then all Maurice events finished (602AD) As the Empire could do nothing to protect the Italians, they invited the Franks to their help (584AD). This first invasion of Italy by the Franks began the process that was to end in the separation of all the West from the old Empire and the establishment of the rival line of Emperors with Charles the Great (800).
I can read it though but I have only Latin text and don't know about any translations. I can read on Latin but it's not so pleasure for me though and I don't know about any translations (Maybe they're exist, but I didn't see them)
This is one of the popular theme now to try to "change" the historical view on different events. Maybe, Maurice had such plans but he haven't even any possibility to think about it seriously because he was busy with Avars and Constantinople economy which became more and more intricate and Maurice became more and more unpopular.
Sure, he tried to do anything but he hadn't time (and maybe brains...?) to figure out what he must to do.
I read History of Byzantium by Timothy E. Gregory, he used many documents and guided by historical source. Good one!