What are the immediate short term and medium term results likely to be (say turn of century). Carlos, for whatever reason does not gain the throne in 1760. Ferdinand persists on the throne for a time yet and the Wall ministry remains in charge of Spain.
Does this hasten the end of the war without Spain's entry? Canada has fallen and the British fleet is turning its attention to France's Caribbean Islands, Prussia is on its last legs, or so it would seem in any case.....Do the French soldier on in any case, hoping that with Prussia's eventual fall they can regain some of their position at the peace. the British after the events of 1760 will be urging Prussia to cut its losses
so that Prussia's loss doesn't undo their own gains.
The Wall ministry will continue to defend Spain's interests most vociferously but is unlikely to enter without being provoked first. They could offer to mediate though. Carlos was Anglophobic. Once he comes to the throne its only a matter of when not if.
So we will suggest that Ferdinand recovers at least somewhat from his melancholy and depression induced dementia at least until the final peace is worked out. Preferably just keep him on the throne for as long as possible such that Spain continues down its steadfast path of neutrality, preferring to be on terms that are not hostile to either the French or the British.