Indeed, the URL redirect in admin will not help you.
You should set the URL in a token, at a folder level that emcompasses all your Landing Pages. Then the token will be available for insertion in all you LP's. When the URL changes, change the token value, and all you Landing Pages will be updated (not even need to approve them).
Just an FYI - I've run into some issues when using URLs in tokens. They work just fine but click tracking in emails typically fails.
Marketo support looked into it on our end and advised us to keep the "http://" local in the asset and only add the remaining URL through the token.