One more time out of nowhere a total surprise popped out while I was lurking the Doomworld forums: The author Revae has posted a thread about his project REKKA a few days ago, that is an Ultimate Doom vanilla TC that takes place in a faux-norse/celtic sorta fantasy world. You beat up monsters, steal their souls, and use their souls to shoot other monsters. It will be a full 3 episode replacement, with the 4th just being "bonus" maps that don't make the grade, or don't fit into the story/theme, or were made after the 3 episodes were finished. The screenshots look very promising so far but I'd suggest you take a look at them yourself.