Would be nice to have different fallback pages that would work based on some words in the URL or name of the original page or URL parameter. We have several types of LPs and each type needs its own fallback page.
You can use Dynamic Content and URL Parameters to change the content on a landing page using URL parameters. Here is more information: https://community.marketo.com/MarketoTutorial?id=kA250000000Kz0h