EDIT: About your suggested scenario, I have a question. Why did the Consell de Cent elect Peter as their king, rather than Afonso V or his brother, Ferdinand of Viseu, who are John's nephews?
Because they considered that his claim came from his mother, Isabella of Urgell, who was the daughter of James II, count of Urgell, the last male descendant of the House of Barcelona. It means they were so angry with John II that they not only decided that he could not reign, but that his entire dynasty (the Trastamaras) were usurpers and should be replaced by a new dynasty. Remember that the nomination of Peter wasn't an Aragonese decision, but a Catalan one. In the election that led to the compromise of Caspe, two of the three Catalan delegates voted for James of Urgell for king, instead of Ferdinand of Castile.
However, I think the scenario suggested by Maniakes is better (after all, Peter didn't have the military strenght OTL to beat John II). You just need to solve the complications it would create for the Castilian succession too.