Get rid of the username in the site url field on wp-signup

So I am not sure, if anyone ever thought of this, or am I the only one. Basically, when a new site is created using the wp-signup.php, the two stepped process asked for a username, and then the site URL. And for some reason, WordPress assumes that the chances of the person creating the site having the username and site URL same are more. Which in my case is not...

I don't want the username to be prefilled on the 2nd step on wp-signup.php. But since wp-signup.php is the core file, I don't want to make edits to it either.

Any suggestions?