Morse is readily adaptable to whatever you can sense: I've experienced it with sound, light, and vibration. Taste, heat, and smell might not work so well.
For input, you need to be able to reliably close and open a switch. This may be difficult for people with tremors, but many accessibility systems are built around single bit inputs, so it's a start. If you can manage another input method, it can be translated to Morse as well.
Internationalization is harder, it's not a good fit for non-alphabetic languages.
Morse code is highly translatable to other senses assuming that the audience had a reason to learn it. I can't think of a single disability with lack of temporal awareness, and only a few with impediments to temporal perception (as you noted).
That said, I don't know ANY blind sea captains. This will be a problem for adoption.