During the tumult of the Hundred Years War, it seems there was also a mini-succession crisis in France; prior to Charles VII being Dauphin south of the Loire, two of his brothers had been heir to the throne, the first, Louis, having died in 1415, and the second, Jean, dying in 1417, either from being poisoned, or from an abscess of the neck.
The second Dauphin, Jean, seems to be an interesting figure as far as politics go. He was married to Jacqueline de Bavière, who would later marry the Duke of Brabant. It was this marriage that had brought the counties of Holland, Zeeland, and Hainault into Brabant IOTL, as she was sovereign of them. The Duke of Burgundy would play a game of cat and mouse with Jacqueline through the 1420s, it all ending with her holdings in the Lowlands being absorbed into the asendant Burgundian state.
So WI the Dauphin, Jean, had not died in 1417? It's unsure how he would handle the Hundred Years War, although presumably he would fight on as Charles VII did IOTL south of the Loire. However, assuming he has children with Jacqueline, this means a major part of the Lowlands will become part of the French crown within a generation. What effects might this have on the Hundred Years War? Of Burgundy? Would these added lands give the French crown the power to defeat the English even sooner, or might it just fumble things all together?