Move login to one page checkout

I am trying to make a one page checkout and would like to have the login, guest checkout and create account options all on one page like in the attached image.
Moving user login under Checkout settings does not work. Is there another way to have the login pane appear together with the other panes?
Also would it be possible to use the billing address form as registration form or vice versa, so that the user data submitted is used for both?