I've been toying around with some design concepts for a DIY submarine for like a decade now. The first thing I thought about, right after "how do I control it going up/down" was "what do I do when that system fails, and I need to ascend in an emergency?" My thought was to have some scuba tanks attached to deployable salvage lift bags, so even if my ballasts were completely screwed, I could still ascend.

If there's not something analogous to that on board the Titan, I'd be shocked at their stupidity; It seems incredibly foolhardy to intentionally go somewhere that no rescue vehicle can recover you, without secondary and tertiary systems in place to rescue yourself.