William AND Mary
You're forgetting the significance of Mary II.
You need to detach the reality of rule post-1688 from the period BEFORE the Glorious Revolution.
It was Mary and Anne who put the groundwork into the Revolution's planning - William was a late and reluctant convert.
More importantly Mary's claim is much more important than William's. She was popular, Protestant, had a nice Protestant husband, and a nice Protestant heir in Anne. And no idea, yet, that the marriage would be childless.
Yes, William has a lot of good qualities, but in 1687 he was a series of bonuses, essentially, that came with Mary. They were a package deal but, to many, she was the more important.
So if you are removing him from the scenario I still think it is Mary, not some other person, who is the best bet. Think about it. OTL England already has an example of a wildly popular and successful female ruler (Elizabeth) and Mary was followed by another successful Queen (Anne) who's husband wasn't really much of a political entity. Mary fulfills the first three of your criteria and, depending on circumstances, could inspire enough of a military force.
Of course it depends on your idea of events - why is there no William III? Is he dead prematurely? Was he never born? If so - what has happened to Mary? Who has she married?
Also, as an aside, whilst Rupert is fetished by many today he was never a particularly popular figure in the 17th century. Its hard to imagine enough people warming to an aged Rupert, even though he is Protestant. Moreover, the House of Palatine was always a source of concern for Parliaments before and after the Civil War - they like that they are Protestants but hate the potential to be dragged into a European war. Which is already happening over the Palatine in 1688.