I’m eventually wanting custom account creation page that includes the info I require instead of just a text box. The obvious catch is the link to user database & emails generation that kiwitrees does.
Unless you want to completely re-write the kiwitrees account creation code, the only way to achieve that is with a custom link that lets new users send those details to you in an email so you can create them as a new user in kiwitrees. There is an example of that here: http://www.zionrootsgenealogy.org/
You also need somewhere to store that additional information. Although I understand that ZionRoots do that just by keeping a hard copy of the emails!