First, one inaccuracy in Wikipedia's article. Reunion to France was an aspiration that inspired some leaders of the Belgian Revolution, but Independence was really the one that carried the majority of supporters, and by far. The description of the exultation of the crowd in Brussels when the French revolutionary flag was replaced by the old Brabant flag in the early deays of the insurrection should leave no doubt about this. Also, before the Dutch responded militarily to the insurrection, there was even the possibility that William I's son would become a sort of Regent for Belgium, and that the two states would remain in some sort of family union.
If Talleyrand's plan had been accepted by the Powers, expect two reactions in Belgium. First, you will need an invasion of the country by all four Powers, which will be extremely unpopular at least in the UK, and to some extent also in France. Second, the Belgian Congress did notify the Powers in London that if the Independence of Belgium was not recognized, the second best solution the Congress would take would be outright annexation to France. So expect Louis-Philippe in a very awkward position: invading a country for which his poular opinion has quite some sympathy, to only keep a quarter of it, when the same country offers itself entirely...
Well, if it still works, expect an even more powerful Prussia to trounce France in 1870, and possibly annexing the French part of Belgium. You'll have no resistance of Liège in 1914 to delay the Germans and allow the French to reorient their armies, and swift defeat of France in 1914. Since the neutrality of the Antwerp Free State would not be violated in such a move, the UK might not have had even the time to join the war...