A Saxe-Coburg king and a possible Iberian union

What might have followed if Fernando of Saxe-Coburg and Gotha became king of Spain?

He could have linked Spain and Portugal through one dynastic household, perhaps allowing a later union of crowns and giving the monarch more leverage in German affairs.

Fernando's Portuguese title came through his position as king consort, so accepting the Spanish crown would not immediately unite both crowns in his person. A son could subsequently inherit the dynastic claims and create a possible route to an Iberian union. That union is treated as unlikely. Even without it, the added Spanish connection could give the monarch greater influence in German affairs.