Just an idea I had: WI the future Charles I of England had died in 1623, while he was travelling incognito to Spain? His sister Elizabeth would be made heir of the throne, but her husband, the Elector Palatine Frederick V was then already living in exile in Holland, after his defeat to the Imperial troops during the early Thirty Years War, and was deprived from the Palatinate.
So, what would happen now, as the Protestant branch of the Wittelsbach from the Palatine become the Royal House of England and Scotland? And how could this affect the 30 Years War?