There are plenty of medieval chroniclers who wrote great works of history. I'm not sure I understand why you consider the writing of someone like Froissart to be more regional or fragmented than Thucydides? Thucydides wrote a book about the war between Athens and Sparta, not a grand, sweeping history of Greece. What makes Thucydides' History of the Peloponnesian War any less regional than Froissart? I suspect that your perception of Thucydides may be impacted by the high regard that modern western culture has for the classical era. It is commonly taught in classrooms that ancient Greece was the "birthplace of Western civilization." Thus, Greek texts are taught in high schools and undergraduate courses across Europe and America, while medieval texts are generally relegated to specialized classes or occasionally an English literature course.

For one thing, Greek was a universal language and that helps. Plus, with the fall of Rome, the western world crumbled into a slew of kingdoms/fiefdoms/whatever with allegiance only to the Vatican, and with different laguages.

For a young scholar, I would suggest a strong grounding in Latin as the Vatican records of that period will be the best for any sort of cohesive research. All those nations were Catholic and in communication with Rome.

Might I suggest a broad topic where the field is still fertile, and you might find a unifying concept?

Chart the growth of the Sugar trade and its influence from the end of the Roman period through its expansion from the eastern Mediterranean to the large Azore plantations using African slaves, and then to the New World where huge plantations were set up in Brazil and other places to produce sugar for the Europeans, again using slaves imported from Africa across the Atlantic.

This has been a largely ignored aspect of western history for political reasons. Original research is needed but that is how a young historian like yourself will make your mark. Hit the libraries at the Vatican, and also Castille and Madrid where old Spanish will be necessary.

IMO the evolution of modern western society can be understood by the insatiable need for sugar, and the capital formation that was a product of turning free Africans into productive "machinery" in the New World.

Be prepared to step on toes. Whose toes they are I will leave for you to discover!