Are there any good
3rd party scenarios that require two copies?
You are only limited by your imagination.
Oh, and there is the maniac 392 page fan-created Space Hulk Missions, which includes includes many, many scenarios converted to 3rd/4th versions. Including some multi-set mission(I think) conversions from video games.
BTW, with Scribed, if you upload a document, you can download one for free.