Could they have plonked the very young Charles I on the throne, and things continue much as they have?
But surely there would have been some incredible power vacuum if Parliament had been destroyed on the opening ceremony, with everyone in there.
Anyone with the vaguest claim to the throne, who wasn't in Parliament that day, trying to seize power?
Perhaps the civil war a few decades earlier?? 
I really don't know enough about the history here - but it's intriguing.