OTL a marriage between Maximilian of Austria and Mary of Burgundy had been negotiated a some points, when Charles the Bold was still alive too. Even an ATL marriage of Mary of Burgundy with Nicholas of Lorraine is far from certain, since Charles tended to use his presumptive heiress as his most valuable negotiation chip. @Cornelis: IIRC Mary of Burgundy died from complications after falling from a horse during IIRC a hunt. IMHO it might happen or never happen, but not likely around the same time, especially since ITTL she's married to someone else, Nicholas.
More surviving Valois branches can have some rather complex implications.
More surviving Valois branches can have some rather complex implications.