Here's a theory that seems plausible...unless I'm wrong. Pelosi steps down and Hillary is considered for the speakership and wins. Biden gets yanked by the 25th and Kamala admits she is unable to take his place because she is over her head. Hillary is now 3rd in line and Viola! President Cacklin' Cankles. Am I nuts? Fire away.
Edit: I have been told the the order of succession changes under the 25th and a majority of the house and senate is required in some fashion. Thoughts.
Yes you are correct, the Speaker does not have to be a member of the U.S. House. Third in line is third in line. To become POTUS the person would have to be a native born U.S. Citizen, 35 years of age and be a resident of the U.S. for 14 years. There are no other special requirements other than that to be POTUS, using the line of succession.