What about Bona/Maria of Savoy for Gaston and Magdalene of France for Edward IV.Warwick will be glad that Edward will choose his side. Only problem! Magdalena of France was married on March 7, 1461. Either Louis XI suspends the marriage while waiting to propose his younger sister to Edward.
I think one possible butterfly is Mary of Burgundy having a younger sister and Charles the Bold reconciling with Nevers, which causes Mary of Burgundy to inherit either Netherlands and her sister just the palatinate of burgundy.What is happen to George of Clarence? George can marry Mary of Burgundy, and rise a rebellion. Earl of Warwick will marry his daughters to the good heirs (there are not Woodville women to invade England). Anne Holland marry George Neville.
No, to Isabella of Bourbon, we can go into a three route with both Isabella and Margaret providing Mary of Burgundy sisters.This sister was born to Margaret d'York. When did she born ? Her name is Margaret or Cicely... Who did she marry ?