By the time of Charles the bold your chances are slim to none- the most interesting time for something like this to happen would be sometime in the early 1420s very soon after Bedfords marriage.
If Philip the good dies hairless at the point where Lancastrian control of France is at its strongest, with John succeeding to burgundy jure Uxoris, that massively changes the political situation. There’s no hope in hell of burgundy favouring the dauphin now, so Brittany likely feels it has to stick to the English side as well. There might be suspicion that Philip was killed by Bedford, and I can imagine a good number of his lords defecting to the dauphin- perhaps a good opportunity to confiscate their lands and reassign them to Lancastrian partisans.
If anyone’s usurping Henry VI later down the line, it’ll be the Dukes of Bedford and Burgundy.
Even with a much firmer grip on northern France, I don’t know whether offensive action against the kingdom of bourges becomes anymore feasible.