Just found this awesome looking Doom 3 mod that creates a prequel to Arx Fatalis (which is also great, play it if you haven’t already). They even written permission from Zenimax/Arkane, so there won’t be any cease and desist bullshit. Looks like these guys have their shit together.
https://www.moddb.com/mods/arx-end-of-sun/
https://www.youtube.com/watch?v=WUNp-gjV7ec
Apparently they’re now working with The Dark Mod to get some asset swapping going, so I suspect that will cut a lot of their dev time out. I hope.