Haha yeah the story is based around a researcher gone missing in a supposedly abandoned castle, and you play a novelist trying to find inspiration for a book and decide to document your search for the missing researcher.
Timed puzzles do sound fun. The last room in Justine was REALLY scary for me haha. Just lookin for what people would find interesting in a mod, and what would make them feel like the story is real, not just searching for X items while running from Y monsters.
Immersion: Your idea for the barracks sounds interesting. I'd have to make use of DonProtz's weapon models
The mountains would be cool too, but it doesn't quite fit the setting and outdoor levels are hard to optimize and make look realistic at the same time.