OTL the industrial revolution started in the middle of the 18th century. Politicaly speaking that was not a good time for Belgium. Austria barely cared for it and Belgium was the stage for various wars in that era. What you need to develop Belgium would be less wars (at least less wars on Belgium) and it needs to be part of a country that wants to develop it.
An independent Belgium or a Dutch Belgium could in theory work, but in those cases France would still want to annex Belgium. So you either need a solid Franco-Belgium or a Franco-Dutch alliance or you need a France that completely collapsed or you need a POD early enough that France focusses elsewhere (like Italy).
Actualy the best solution might be a French Belgium, but the French political situation needs to drastically change from what is was OTL. You need more political and economic freedom in France, like there was in England or the Dutch republic OTL.
Edit: BTW for a Dutch Belgium that starts the industrial revolution, you actualy need a different Netherlands in the 18th century. The Dutch republic OTL didn't want all of Belgium, it would need better rights for catholics (or you need a protestant Belgium, thus needing a POD in the 16-early 17th century). To be fair, I think it is easier for the Dutch Republic to change than it was for the Kingdom of France.