I am a WP Newbie, so forgive any errors in my thinking. However...
It seems to me the "User Registration and Password" aspects of WP would be better moved to the files generally created and worked on in the basic theme files, and away from the Admin class of files. Isn't the user registration and password management part of the basic user interface?
I am currently building a theme based on the default theme but find all of the user registration files buried elsewhere. How can these be moved (e.g. wp-login.php) so they don't get blasted by upgrades? And I am going to try changing the .css file so the basic theme style sheets are used in the log-in and user management processes.
Am I wasting my time here? Am I on the right track? Have others already worked through this so that their user registrations are easily 'themed' along with the rest of their site?