Would like all wp-signup elements on one page


I’m trying to make signup to my multisite as easy as possible. I’ve followed MasonJames’s suggestions for making a custom wp-signup (at https://premium.wpmudev.org/forums/topic/wp-signupphp; thanks!) and they’ve worked really well.

What I’d like to do now is get all the signup form elements on one page (instead of two, as per default). I’d like my customers to put all their info in one form, and click one submit button rather than going through two steps. Can anyone point me in the right direction, or do I need to provide more detail?