I think that a three kingdoms Spain is the best option.
If Peter II of Aragon crushes Simon de Monfort army and negotiate the reintegration of Catharism into Roman Catholicism ( probably needs to kill the leaders first and then he can be more lenient whit the peasants) he can start to truly unite Toulouse and Provence with his Iberian possessions, moving people from Toulouse to the Ebro valley and creating the basis for is son James I Crown of Aragon to become the main player in the Mediterranean.
In this scenario France doesn't have direct access to the Mediterranean, so Aragon would probably had a easier time conquering Sardinia, Sicily and Naples.
From there, Tunisia and coastal Albania are doable, creating a barrier to the Ottoman expansion into western mediterranean.
Castile can take Navarre and prevent a french dinasty from taking the kingdom and eventually expand into southern Gascony, taking the basque speaking region and Bearn.
In this scenario, Castilian language would in time replace basque and gascon and just like Aragon would seize any instability in France to further centralize and promote the language shift from basque and gascon to castillian.
Castille would fallow Portugal into the Age of Discovery but due to a longer reconquista whit a delay of several decades, so Canary Islands go to Portugal but Orania and Algeria are seen with interest and we probably see the conquistadors first in North Africa and then in the Americas.
In the west, Portugal and Leon unite and are the first to end the reconquista in Iberia , consolidate, and expand first to the islands and then to coastal Morocco.
Portugal establish a colony in Newfoundland and goes on to settle north america down to Delaware and Castille establish the colony of New Navarre north of New Castille (Mexico) and in time, indigo, rice, tobacco and cotton and the settlement in the american Piemont, healthier for europeans would create a wealthy colony and then a Vice Kingdom.
In South America, Portugal settle in coastal Brazil but in time reach the Pampas and Otl Buenos Aires becomes the main population center in Portuguese South America and while the castillian silver is exported from Lima to Asia an agreement with Portugal allows Castille to export silver to Europe from Otl Buenos Aires in exchange for the portuguese right to settle in Chile.
Castilian silver would finance the Portuguese expansion in the Indian Ocean allowing for someone like Afonso de Albuquerque to lock the Ottomans out by taking Aden and gaining influence in Abyssinia and Aragonese expansion in the Mediterranean.
Eventually a two prong attack by Aragon in the Mediterranean and Portugal in the Indian Ocean would crippled the ottoman navy and the Ottoman Empire would be on the defensive.
A Spanish Commonwealth could emerge as a loose confederation due to common interests, but the kingdoms would remain separate and brides would be chosen in the northern Italian states from families like the Sforza, Farnese, Medici, Gonzaga, etc,
Aragon focus and dominates western and central mediterranean, Castille becomes the main player in the Americas and Portugal establish the sea route to Asia and hires Magellan so no Philippines, they are called Fernandines and belong to Portugal.
The Iberians have a decent chance of only loosing some islands in the Antilles to the English and French, but in India, Portugal settles in the west ( Konkan, Malabar and Ceylon) and the French take Madras and the English, Calcutta.
If Portugal arrives soon enough, part of Java can be converted creating a strong colony and a base for war with the sultanates like Malacca, Aceh, Brunei and a second base in Manila in the Fernandines would allow power projection into East Asia and Macau, Tamão, Amoy, Formosa, Okinawa and Nagasaki could become part of the Empire, especially if Portugal is strong enough to help the Ming resist the Qing.
Maybe after being defeated the remnants of the Ming convert to catholicism and flee to Formosa, Fernandines, Java and Malaya.
No jewish expulsions, quite the opposite, the Iberian kingdoms become a safe haven.
Both Portugal and Castille would take advantage from the potato famines in Ireland and Scotland and settle thousands of refugees in the Americas.
View attachment 692094
My two cents to the discussion......