Apologies if this is already covered somewhere, but I didn't see it.
The gist is in the title: I took a quick crack at creating a tool (based on previous work I've done for Empyrion) that will import a 3D model into a prefab for 7 Days.
It is open source (link), and extremely early stages, but it's built on about 90% re-used code, plus a bit of reverse engineering of the TTS file format, beyond what is in the wiki.
If there's a strong desire for more features and a better implementation, I'm open to suggestions from folks!
Here's a quick video showing the result of importing The Hive from Resident Evil:
