I know the idea is a very unlikely one but stay with me. Lets say cooler heads prevail in the Cortes that meet after the 1820 liberal revolution and they don't try to demote Brazil to a colony again or John VI unilaterally tells them no. How long would the United Kingdom of Portugal and Brazil last? Where would the king rule from and who would rule the kingdom that he is absent from? Perhaps the Monarch rules in Portugal and the heir rules Brazil?