You may be familiar with Stone Abyss, a “scripted remake of original JJ2 story” that certainly is one of the better custom single player episodes uploaded in recent years. It started out as a small three-level pack, but has grown considerably in size and sophistication since it was first uploaded in 2014.
Now Bloody_Body has uploaded what might be the final (major?) update to his episode, bringing the total to 12 levels and tweaking the difficulty and mechanics a little as well. Sounds like this might be the definitive edition, so you owe it to yourself to give this a try if you haven’t yet. And also if you have, since chances are there have been some improvements and additions since you last played it.
Check the download page for the details and don’t forget to leave a review once you’ve played it!