Slitherine

I am currently reading about the fall of the Ottoman Empire.

This got me wondering if there any Great War mods for OOB.

I think OoB would need some significant adjustment to its gameplay mechanics to simulate the Great War. For one, entrenchment would have to be more significant, semi-permanent, and allow for rotated units to maintain the entrenchment levels on the hex they move into (sort of like Commander: The Great War). In general, I'm not sure if the format of OoB would lend itself well to position warfare with mostly static front lines (even the comparatively more fluid situation which existed on the Eastern Front and the Near East.

The Russian Civil War and related conflicts, on the other hand...

I agree. I doubt that it would work.