OK, this is my short start of TL:
So, Miguel dies in 1821. Cortes is still in session- working on new Constitution. The Queen is heavily hit with the news of Miguel's death ( her favourite son ). Pedro stays in Brazil, but is also hit with his brothers death. In meanwhile, independence movement in Brazil is stronger and stronger. Cortes asks from Pedro that he returns from Brazil. Pedro refuses- out of fear of dissolution of Brazil.
In meanwhile, Cortes works on new Constitution. The Queen while opposed to the Constitution is not so much into politics because of grief for Miguel.
So, Cortes accepts new Constitution, Joao VI takes an oath to the Constitution. Brazil refuses the new Constitution and independence war starts. After few years ( as in OTL ) Brazil wins and Portugal accepts his independence. Cortes, angry on Pedro because percieved his main role in independence of Brazil, decides that Pedro has lost his sucession rights in Portugal by becoming the Emperor of Brazil ( another country ).
In meanwhile, Joao VI dies in 1826. So Cortes pronounces his sister, Infanta Isabel Maria becomes the new Queen of Portugal in 1826.
Queen isabel accepts the liberal Constitution and the period of consolidation happens in Portugal. Queen Isabel Maria searches for husband in Europe- she wants to ensure the offspring and sucessors for her dynasty. Conservatives, without Miguel, easily accept the status quo and Constitution and start to act trough Cortes. So we have three main parties in Portugal: Liberals/Vintistas ( for even more liberal Constitution and liberal reforms, universal suffrage, responsible Government etc. ), Conservatives/Regenadores ( for absolutism ) and Moderate Liberal Party ( for Constitution of 1822 )...
What do you think?