You are right, Jonas. In the previous post we have focused on Elisabetta Farnese.
But you have to consider that, probably, the Louise Maria Therese Stuart of this scenario is
different from the LMT of OTL
For example, a simple reasoning could lead to some considerations about the possible difficulty in choosing of LMT as a bride for Joseph Ferdinand Leopold of Bavaria as King of Spain.
JFL comes of age in 1706, and from that date forward we can think of a marriage for him.
But what has happened in European politics between 1700 and 1706?
1. How JFL was chosen to be the heir of Charles II of Spain?
=> [unofficially] in the Treaty of The Hague (or First Partition Treaty), a SECRET arrangement between the England of William III and the France of Louis XIV to prevent the outbreak of war at the Charles II's death.
very important: It was an informal approach between Louis and William.
# Reasons for signing the treaty:
+ for William: a) avoid a chaotic situation because there was no a clear successor to the Spanish throne; b) Spain and the Spanish Netherlands [important for the United Provinces] would remain independent;
+ for Louis: a) the power of France, in any case, would significantly increase due to the Italian possessions; b) Louis therefore would have had the peaceful acquisition of Spain's Italian possessions.
Real Reasons:
+ for William:
a) the real English/Dutch interest was purely for the benefit of their business interests: to exclude the French pretender (= to exclude the competition of the French enemies in the English/Dutch trade with the Spain) and the imperial pretender (in age rule alone) it meant to keep the Spanish monarchy weak (JFL was under regency until at least 1706) and to favor the English/Dutch commercial dominance (the commercial intercourse with Spain and her dependencies was indeed highly important; a considerable number of British merchants at that time lived in many ports of Spain);
b) the English/Dutch public opinion did not wish be disturbed by the Spanish question in their trade with that country and its colonies;
c) England, now that it had just ended the war against France (Treaty of Ryswick), wished a lasting peace: the Commons passed a resolution that all the land forces raised since 1680 should be disbanded (the old aversion against a standing land-army!) and the dismissal of Dutch troops whom the King William had brought over with him from Holland and still paid by means of his Civil List
=> William was militarily weak
+ for Louis:
a) at only a few months since the Treaty of Ryswick, Louis had the wish to preserve France from a new war;
b) in September 1698, at the conclusion of the negotiation, it was clear to Louis that in Spain the time was not yet ripe to accept the succession of one of his grandsons, because none of the Grandees wished this, and none force was ready in Spain to support the French claim. And in the case in which he had taken by force the kingdom, the other Powers would have formed certainly a league against France;
# implicit importance of the treaty:
even if the Emperor Leopold was not invited to the negotiations and although JFL looked like a "middle way", the treaty was a victory for the English policy against France, and consequently, a victory of the Habsburg policy because:
1. acknowledges the two formal acts of renunciation of Maria Teresa, wife of Louis XIV, in which she renounced all her hereditary rights on the dominions of her father, for her and for her descendants male and female, in order that it could not happen to unite the Spanish kingdom and other territories under the sceptre of King of France [mitigated in the treaty with the award of the Italian territories];
2. acknowledges for valid the provisions of the Will of Philip IV (confirmed by the Cortes of Spain), who had expressly stated in his testament that, after the renunciation of the eldest daughter, it was in the person of second surviving daughter Margaret that would be assigned the rights to the Spanish throne after the eventual death without heirs of Charles II
=> Louis and William consider that the Electoral Prince JFL, when of age, will not object to the renunciations imposed on him by the Partition Treaty, if this treaty should be the sole source of his right;
=> [officially, after that the Court of Madrid has become aware of the Partition Treaty] the Will of 1698: King Charles II had appointed the Electoral Prince of Bavaria his successor to the Crown;
+ Charles II and the Spanish Government , independently of the Partition Treaty, have the idea to recognize of the rights of the Electoral Prince JFL as a means to transfer ALL dominions of the Crown of Spain from Chailes II to his successor
+ the idea of a partition of the Spanish monarchy is refused with vehement indignation by the Spaniards: this document was an attempt to save the integrity of the monarchy from the danger of being dismembered from the agreement between France and the other Powers.
=> the Will of Charles II in 1698 confirmed at the same time the testament of Philip IV. In case of a minority of the future King, Queen Mary Anne was to hold the regency together with a Junta of six persons.
2. If the succession of JFL has taken place, a general war would really have been avoided?
=> probably, but...
+ Louis knew that William had none hope of carrying English Parliament along with him to a war against France after the last parliamentary decision to dismiss the land forces...
+ the Ministers of the Emperor Leopold, formally, were ignorant of the contents of the secret Partition Treaty between Louis and William...
=> Leopold accepets the Partition Treaty? [originally Spain, colonies and the Belgic Provinces to JFL, The Italian dependencies (kingdoms of Naples and Sicily, the places belonging to Spain along the Tuscany coast), the marquisate of Finale and the Spanish province of Guipuzcoa, contiguous to France, to the Dauphin, duchy of Milan to Archduke Charles, the second son of Leopold];
=> It's doubt that he is content with only of duchy of Milan...
(Wikipedia.en articles have mixed the provisions of the First and the Second Treaty of Partition, "have forgotten" the secret article that claimed to the succession JFL's father in case of his death, the project of territorial exchanges proposed by France (June-August 1699) before the Second Treaty [Treaty of London (1700)], but after the death of JFL, are placed in the First Treaty [Treaty of The Hague (1698)], etc.)
=> probably a mini-war between Austria and France for the Spanish Italian possessions...
+ large diversity of interests:
a) Leopold wished to secure for his House the Italian possessions of the Spanish Crown;
b) the Maritime Powers not wished the French competition in their trade with Spain and her transatlantic colonies;
c) for Holland it was important that the Belgic Provinces, a valuable barrier against France, did not pass to France;
3. If JFL becomes King of Spain:
=> no Second Treaty of Partition;
=> no new Will of Charles II (October 1700) in favor of Duc d'Anjou (to inherit the whole Spanish monarchy, with all its world-wide interests and possessions undivided; no part of the monarchy should be alienated and no part should never be united with any other foreign State, against the policy of the Partition Treaties);
=> in OTL Louis XIV accepts the Will of Charles II and fails to comply the Second Treaty of Partition;
=> no Maritime Powers considers Louis XIV a great danger;
=> no union of the French and Spanish navies
=> there is no danger in the opinion of the English and the Dutch;
=> probably no William's/English foreign policy of OTL;
=> probably no Grand Alliance (1701) to the establishment of the general peace [in reality only because England and Holland would like acquire security for their dominions and for their commercial interests!];
=> In this climate and in these good relations, the relationship between Louis and William could have been better: the informal approach at the secret Partition Treaty, could become formal; though since 1697 William had been acknowledged by French diplomacy as King of Great Britain, yet this acknowledgment had been given only implicitly, not expressly, by Article IV of the Treaty of Ryswick between France and England;
=> Louis could decide to not acknowledge the son of the deposed James II as King James III of England, Scotland, and Ireland (1701) [In OTL when Louis has accorded to the son of James II the title of King of England, the English patriotic indignation rose to a height which it had seldom reached before];
[=> the English are less angry, no Act of Settlement?]
=> certainly/probably, in 1706, without even the formal recognition by France of Louis XIV, Louise Maria Therese Stuart would not have a political importance such as to be considered a candidate to marry the King of Spain.