Hey Grant! I love the idea! It could be very useful. First of all tho, your personal sayHey is dead: https://sayhey.to/grantfwilkinson
I think it doesn't look good, because it brings me an impression that it's buggy and the same can happen to my landing page.
Secondly, I would love to first try the builder, then sign up an account to publish it, because now I'm not sure if people will go through registration process without have an experience with the app.
That's small feedback from me, love the idea anyway and wish you good luck! 🙌