When the Spanish Empire set about on reforms to it's administration both in Spain proper and abroad in the New World, during the 18th century, the Crown attempted to increase the efficiency and output of it's colonies...except that it was not enough in the end. France and England still managed to eclipse the once powerful Spanish Empire during the course of the century. What went wrong? Yet more importantly, how could have the Spaniards been more successful in their colonial and administrative reforms?
The Spanish were very hesitant on removing their monopolies or economic restrictions that made no sense.
In every sense of colonial policy, the Spanish attempted to have some sort of strict regulation that crippled development. For example, maritime trade must be conducted in a specific port in the region, (Veracruz, Santo Domingo, etc) and shipped to specific Spanish ports in the south of the country in Andalusia.
This of course means every other port was neglected in infrastructure, weakening any growth of mercantile elites and the general diversification of the colonial economy thanks to a lack of demand.
Oh and the lack of inter colonial free trade seriously hampered development, as the only market to sell goods to was either internal (problematic given the tiny population of Spanish America outside of the Valley of Mexico and the Andes) or to Spain. Officially of course, smuggling was absolutely rampant due to the insane demand.
For Spain, the restrictions hurt the country as the Green Coast, despite its number of ports was unable to capitalize on the colonies' wealth and markets. And the restrictions on any other than Castilians moving to the colonies (for a very long time) didn't allow for a 'pressure valve' of sorts that would spare the country from some civil strife along the road as it did in the English colonies.
Basically, the easiest way to improve the Bourbon Reformation would be to loosen restrictions early on, instead of during the reign of Carlos III. Have a king or minister focus more on free trade, and allow for the end of the inter-imperial restrictions and monopolies on trade. The colonies trading with each other would drastically help their economies out, which gives Spain more money via tribute.
To alter that, you'd need a POD based around...the reformation succeeding in Spain in the 16th century? Probably the Sephardic Jews not being picked up by the Ottoman Turks in 1492. Of course, you'd need a rationale for why Isabella and Ferdinand had a sudden bout of tolerance. The other possible POD would be discovery of mineral wealth.
The Reformation succeeding in Spain won't intrinsically change the system of regulations that Spain had in its economic system. It will simply transfer Church assets to the government and nobility, which might make later reform even more difficult given Spain's feudal tendencies.