Interesting idea, of course from my experience of hacking through the WP code, there is an awful lot of hardcoded references to the admin folder.. But I don’t know that much about WP so maybe. Since the result of moving wp-admin to wp44-admin would be they would start using bigger guns and attacking everywhere, it might be better for the server resources if WP developers just added a lock-out after so many attempts.
The problem that I have seen in the past with that type of setup is when they build it all into the database.. whcih effectively just gives you a slower site.
One way you could make apache and WP do this is by having .htaccess code that denies access based on the value or presense of a cookie, which mod_rewrite can see in the Set-Cookie HTTP header. So after 10 bad login attempts the login script stops providing the robot with the correct cookie, thus locking them out.