I think most of Europe would have had the same reaction (now, if they were cousins 
). It would have enabled Mary to ascend the throne and Fitzroy would’ve likely taken the crown matrimonial and become king jure uxoris. One of the big issues with a queen regnant is that she would’ve been expected to marry and produce heirs of her own (though Liz never did). There was no precedent in England regarding a male royal consort. When Mary I finally did marry the future Phillip II of Spain he took the crown matrimonial and was styled King of England and, unlike a queen-consort, had official acts dated in his (as well as Mary’s) name, parliament was called under their joint authority, etc. But as he spent most of his time in Spain he didn’t exercise any real power. Neither did he remain king after Mary’s death.
I read once that Jane Grey’s husband, Guilford Dudley, was also styled “King” or “King Consort” for the nine days Jane reigned, but I can’t find that in the linked article.