Personally, I think I'd need the following features for a landing page.

• Custom branding
• No automatic page-turning; thus, no timer
• I need to see how people interacted-with/answered my questions.
• I want to build a tree of answers that lead to other questions, maybe even other Once stories.
• I need to be able to capture their email.

How far along are you? You might already have these features, so I might be saying things you already know. 😁