I'm currently going through something similar myself to get back my medical status for offshore oil adn gas work. There are OGUK (Oil adn Gas UK) guidelines that I need to meet such as stable condition for at least 6 months, no hypos needing outside assistance, good hypo awareness, self testing adn management etc but also each individual platform operator needs to approve up front and to have medics and facilities suitable to treat hypo and hyper glycaemia.
In my case, I could be medevac'd and into hospital in 2 hours or so if necessary.
If I were you I'd be looking for industry guidelines which may come down to the flag state for the ship, and also thinking about the "what if's"