Hmm... I, at least, find Burgundy (as a continental power, possibly trying to recreate the Empire of Charlemagne?), Genoa (as a potential colonial power, with the historically hired out Italian explorers such as Columbus) and Hansa (as something of a hybrid of the two, and as an obstacle to Kalmar domination of the Baltic) interesting, and Hungary possibly as well (in the role of the falling empire, perhaps, with Byzantium, Bavaria, and Bohemia profiting from its decline, and then trying to arrest its own decline by going CRC and trying to force the region's heretics back to Catholicism). If it's just an issue of nobody yet stepping forward to write events for them, I suspect that might be an issue of language (it's rather difficult to research this period of history without speaking the language of the country you're looking at).
I agree with Milan (too close to too many other powers) and Ukraine (too close to too many small states, will rack up BB like mad).