an interesting WI
but ultimately hard to see how much really changes. The main players weren't dynamic enough to lead Brazil (and drag Portugal) into a progessive state. A best case scenario leads to portugal accepting a secondary role. A semi-realistic case leads Brazil and the colonies to separate from Portugal. A worst case leads John and his heirs to losing the crown . Let's accept for argument's sake the best case. John stays in Brazil. He keeps a significant military/navy. This allows for a victorious cisplatine campaign, but beyond that, what really goes well for them? Brazil is a backward, ill developed country. With inspired leadership, there's a possibility Brazil progresses far beyond what they actually did, but there's no indication any of the crown has what it takes to do anything more than what Pedro 2 did - keep stability enough for the planter elite to maintain their hegemony. Likely a successful state, but not a power.
Now, if the WI were a dynamic John and/or Pedro, you might see an interesting development, but the first was a reactionary, and the second didn't have the temperment to conciliate his way to a bright future.