Maybe the following could happen: the Dutch recruit a lot of troops in the South and send these men overseas. With the Belgian revolution, the Dutch East Indies army rebels, overthrows local Dutch rule and seeks support in Belgium. They offer the National Congress sovereignty.
The Brits, anxious to have a strong Belgium support this claim. The English hope to convince the Belgians to let British companies do the transportation of goods between Belgian Asian holdings and Antwerp, this would strengthen English hegemony over the seas. The French, who hope that if Belgium gains a colony they'll get eventually, are keen too.
The National Congress feels strong enough to accept, and the Dutch East Indies are to become Belgian.
However, the Dutch launch the 10 day's campaign, defeating Belgium. In the new treaty the Dutch East Indies are divided: Belgium receives Sumatra, including a claim on the parts not yet under Dutch command and the Dutch keep the rest. Belgian revolutionaries want to keep hold on Java, and occupy Batavia, but some gunboat diplomacy, and the ratification of the new treaty by Belgians and Dutch in 1831, force these men to move across the waters to Sumatra.
In the Dutch indies, the situation escalates:
The Dutch have to fling themselves in a new series of costly Java Wars. The Belgians on Sumatra too have to pacify the natives.
The West Indies: Belgium receives land from Guatemala like LSCatilina points out. Because of the situation in Sumatra, the Belgians do nothing much with the area. But once the pacification wars are over, the experience from Sumatra is used to build a new colony in Guatemala in the 50s.