Eric, when you know where the password field is, can't you the look for the username field in the same form. In other words, the form will be something like this:<form name="xyz" action="zse.asp" ...
<input type="text" name="username" ...
<input type="password" ...
<input type="submit" ...
</form>
By knowing where the form is, you should be able to extract the username field. That should eliminate a lot of useless fields on the same page.
But then, I didn't mind the way you did it in 0.8.0. If you refine this a little by requesting that the user click on the username field, when setting up an account. Then, when the user clicks in the username field, you just capture the click event and grab the name.
I do not know if this would be possible, but I thought that I would throw this idea your way. Who knows, may be that'll kick something into gear in your brain.