I have several small suggestions for improvement:
1. Alternative scenario- you would start at the bottom of a cavern system (perhaps cutoff by a collapsed passage) and you would have to find your way out, better yet, the water level in the cavern system would rise slowly so you could drown if you don't move fast enough.
2. Alternative scenario- rescue mission - you would enter the cave trying to find spelunker that went inside before - following sporadic marks on the wall, again the water level could raise slowly so you would have to move quickly.
3. Dynamic ropes- I haven't figured out the current system completely, but it seams that if a rope is attached between two pitons and I reclaim one, the rope will vanish or stay, sometimes the rope will stay in place even if I reclaim both pitons. I would like to see this- if I reclaim a piton the rope would freely swing and hang from the remaining piton, if you are holding the rope you would swing pendulum-vise until you lose momentum and end up hanging.
4. Being attached on the rope- as a safeguard, you could deploy a piton and attach yourself to a rope, if you fall, you would be left hanging on the rope.
5. Overview of how much pitons and rope length is currently deployed.
6. Flares/breaklight that could be thrown down holes - the screen would be centered on the flare for a short while instead of the player exposing the cave as they fall.
7. From reddit forum- optional inventory system- how much pitons ropes and air tanks are you carrying, high weights could impair grip endurance.
8. Ability to actually exit the cave.
Any more ideas?