FluentAuth suggestions needed

Hi everyone, I have all the pro versions of Fcom, FForms, and Fcrm. I have a private space I want only people with a specific bonuscode string like "FREEBONUS". I would like them to be able to get into the space in 2 ways:

1. If NOT a site member yet - using a URL that takes them to my site and the bonus space, see a form to both join the site AND put in the bonuscode, get redirected back to the bonus space.
2. If already a site member, then just click on the space and be asked for a one time bonuscode in a form.

I realize that the access is done by fluentCRM tags. What is messing me up is that I can't edit the registration form from FluentAuth.

Can I just use fluentform to make my own unified registration + bonuscode form?

I guess I am just confused. I love the magic link and code functionality and don't want to mess that up.

I opened a ticket on this just now, but they may not get what I am trying to do? It is not a bug, but a best practices question really :)