I don't think he was suggesting switching hosts but domain registrars. Not only does Blogger let you bring your own domain from any registrar while hosting with

I don't think he was suggesting switching hosts but domain registrars. Not only does Blogger let you bring your own domain from any registrar while hosting with them, but they stopped selling domain registration themselves at some point in the past. Transferring the domain should be completely transparent to Google; the website doesn't need to move or be changed at all.