It could be mounted externally, separate from other systems, and it would be fairly trivial to implement a strictly mechanical means of activating it from inside the vessel. All that would be needed is to open the valve on the external pressure vessel.

If you’re referring to getting out once you’re on the surface…hell of a lot easier for rescue crews to find you and do that if you’ve got a huge orange inflatable holding you at the surface, rather than however many thousands of feet underwater.

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.