Doubt it Norfolk presided over his niece's trial - he knew which side his bread was buttered!
Did not remember that. Oh well, there goes my dream of a surviving Fitroy marrying his slightly older, unmarried until 1544 IOTL, cousin Margaret Douglas. Frances Brandon was already married to Grey 1533 and Eleanor to Clifford in 1537.
Assuming he lives then he will undoubtedly play a huge role on Henry VIII's death possibly preventing both the Seymour's and the Dudley's gaining so much influence under Edward VI.
How smart a player does he turn out to be is then the question. He will be 28 or so when H8 dies. Will Fitzroy be independent or will he initially rely on the counsel of the likes of Edward Seymour, or worse Thomas Seymour? Does Dudley still rise high so that his mores sensible (but still grasping) opinion is taken into much consideration?
If Fitzroy is still married to Mary Howard, does Thomas Howard (3rd Duke of Norfolk) get released from the tower any time soon after H8's death. Howard died in 1554, being released from the Tower by Queen Mary. Could he possibly have influence. Or his surviving son, also named Thomas?
Who else might be well positioned to catch Fitzroy's ear?
I could see an inexperienced, poor playing Fitzroy loose influence, or even a place, on the Regency Council. But unlike Seymour (Somerset), do to his blood, I can't see him being executed for losing such.
unless Richmond fell out with his father before his death I have little doubt the King would have named him in the mix - the question then becomes the undoubtedly illegitimate Richmond (who is at least male and by 1553 probably a father) or the two female's both of whom were born to woman acknowledged as Queen's but who were declared illegitimate by statute.
Fitzroy would definitely be in the mix for the crown, but would he get it? That is where I see a marriage to one of his Tudor cousins as rather a powerful multiplier. If he did, and they had a son, perhaps he could claim the throne in the child's name.
I guess a lot might depend upon how well the perception of his time leading the Regency Council for E6 was?