So since things in Belgium look to be on their way, what happens in the Netherlands. While we're stuck with Willem III (as he's already been born by the POD) maybe we can prevent his disastrous marriage with Sophie of Wurttemberg. Perhaps Duke William of Brunswick, who apparently also sought Sophie's hand, manages to get his suit in before the Dutch betrothal, causing the Netherlands to look elsewhere?
This could be big because, if Willem leaves a legitimate male heir to succeed him instead of Wilhelmina then we never see the split of the Netherlands and Luxembourg. Plus a generally happier marriage could change Willem's approach to ruling in general.
If we change Willem's marriage, here are some candidates, in no particular order
- Princess Maria of Wurttemberg (1816) - Sophie's elder sister
- Duchess Amalia of Oldenburg (1818)- OTL Queen of Greece, had infertility issues
- Duchess Frederica of Oldenburg (1820)
- Princess Louise of Schleswig Holstein (1820) sister of OTL Christian IX who became an Abbess
- Princess Marie of Saxe Altenburg (1818) OTL Queen of Hanover
- Princess Pauline of Saxe Altenburg (1819) short-lived sister of the above, died after POD
- Princess Mathilde of Schaumberg Lippe (1818)
- Princess Adelheid of Schaumberg Lippe (1821)
- Princess Louise of Hesse Kassel (1817) OTL wife of Christian IX
- Princess Marie Amelie of Baden (1817) IOTL ended up converting to Catholicism in the 1850s, could be butterflied away
- Princess Caroline of Hesse Homberg (1819)
- Duchess Louise of Mecklenburg (1818)
- Duchess Caroline of Mecklenburg (1821) OTL Queen of Denmark
- Princess Alexandrine of Baden (1820) OTL wife of Ernest II of Saxe Coburg and Gotha and one-time fiancee to Alexander II of Russia
- Princess Catherine of Wurttemberg (1821) half-sister of Sophie