Moving landingpages between Sandboxes

[#1]

Today: Landingpages are used for opt out (unsubscribe) to emails. Link to this page is placed in a email fragment in the footer of all email. A standard way of doing this. When this link to this page is created in the email designer tool, it adds a landing-page-id to the link. This in a unique ID that need to be there present for the link to work. 

And here comes the challenge .... 
If you use a Sandbox for testing, that many do. We have all our email fragments present in the test Sandbox. And it you then have created links to a landingpage for opt out, that page does not exist in the test Sandbox, or the other way around.

The problem:
We are running into a problem either way we look at this. If we create the link to the opt out page from the test Sandbox, this will not work when moving the fragments to a Prod Sandbox. Or if the link is created in Prod it will not work in Test. The result of not having the right landingpage present in eighter Test or Prod we are not able to send Proofs. 

The need:
It is not a sustainable solution that we need to change the landingpage-id in this out out links to get email fragments and Proof sendings to work, when working with a test and prod environment. Especially when you easily can move fragments and templates with no problems between Sandboxes. But in most cases it is a link in a footer fragment that will not work if you aren't able to move the landingpages as well.