What did you have in mind? I can't say I'd be able to contribute as I'm already working on two mods. But I would love to hear what your idea was and maybe discuss techniques to do with world space formation.
I've made a separate worldspace that ties into a mod in Skyrim. It's not very big, 7x7 cells (a little bigger but everything outside of that is water or icebergs). I didn't use any generation tools like l3dt and heightmaps, I just sculpted it all by hand. It has been fun but it was an enormous time sink (if I could start over I'd do it differently). I have reiterated over it so many times, worrying that it was too flat, too sparse etc.
An idea that I had that must involve a separate worldspace (but not an alternative to the main game start). This isn't one of the mods I am working on currently but maybe for the future. (I've written dialogue for it but done no work in the CK )
I really love the Brotherhood of Steel and I have this huge role play desire to be a scribe in their ranks. What I imagined was adding a new officer aboard the Prydwen that assigned missions for aspiring scribes. You would be a scribe with a group of Brotherhood soldiers who effectively acted as your bodyguards on a mission. You're the brains, they're the brawn. You would board the vertibird on the deck of the Prydwen and a prompt asks if you're ready to undertake that mission. Assuming you do , load screen to you and your team aboard a vertibird coming in to land at the location of interest. Which would be a relatively small worldspace bounded by the Bethesda style obliterated landscape you see around the glowing sea and the "you shall not pass" scripted collision planes to ensure you don't wander too far off mission. The size of that space would differ from mission to mission but nothing too big. As for the mission I envisage it more about getting to know the team you're with. Some of them might be the typical BoS hardass, others much more relatable. And I think a cool metric for mission success would be how many made it back alive, despite the hostilities encountered or, more importantly, any story driven infighting during the mission.