The only reason why Luxemburg was in personal union with the Netherlands was because both Prussia and the Netherlands wanted Luxemburg. The personal union was basicly a compromise between the Netherlands and Prussia so that both could have influence over Luxemburg, The Netherlands through the union and Prussia through the German Confederation. In my scenario I don't think Prussia would force a Personal union for some rather unimportant areas.
Ok, in that case I need a better way to get rid of those areas. Although, to be fair, I think a referendum in or around the middle of the 20th century would probably work. But since I said I wanted them not part of the Netherlands in 1900, I need to think of a better way.
I was talking about Belgians, don't they hate the French as much as they hate the Dutch? Ok, maybe I misstyped.
Sorry to object but Luxembourg was a compensation to the House of Orange-Nassau for the loss of the German lands of Nassau. Hence Luxembourg was only in personal union with the rest of the kingdom of the Netherlands.
Prussia, Austria and Russia had much more inserted than only the former Austrian Netherlands. Prussia was far more interested in foremr kingdom of Saxony and there Rhine holdings while Russia wanted more of Galicia. If you want to have a large or different united Netherlands you need to see it in a more broader picture.
I like the idea of a dead Taylerant.
I can not recall that the Belgian revolt was popular in Luxembourg as it was in Brussels and Liege.
A major thinking error, if to put it this way, is the language question. The language dispute in OTL Belgium is solely the result of the language policy since the Belgian independence, where the Dutch became marginalized by the French speaking upper class making French the only official language of the government in all its levels.
The French language is not bound to a territory. In the 19th century and even up to the 20th century French was the preferred language of the upper class and of the Catholic clergy. French was also spoken by the upper class in the Protestant North.
If a united kingdom, with the French provinces survives a social unrest in the 1830ties the language difference will be minor compared to religious differences which will emerge.
If it stays united, the French will be recognized as official language of the Waloon provinces as in OTL. There will be a labor emigration of Dutch speaking people to the industry areas in Waloon. In OTL they influenced the French, but it remained Frenc,h since it was the official language of Belgium. In a united Netherlands French will only be the official language of the Waloon Provinces, which give a possibility that the Waloon provinces with a high migration from the North will gradually change in Dutch speaking provinces. A reversed move of the language border as in OTL happen with Brussels.