It would be useful to have the ability to create multiple custom domain names for one app.
For example, you have Company A, Company B and Company C using your app, and you’d like to create custom forms for each of those domains. You’d add a sub-domain for each of those apps on their main domain name (e.g. forms.companya.com) and then create a no-layout page that can be accessed via a link on their site (e.g. forms.companya.com/companya-form). That way no one knows they are using the app. Looks like a form hosted on their server.