There are various plans out there that can take care of medical emergencies, return of your coach AND your PETS, as well as getting your remains back home.
If you have one of these types of policies, it doesn't matter who can drive or not. They will take care of things.
Basically the answers for all of your concerns can be addressed by examining the different travel insurances that are out there. It is one of those things that is best taken care of early when you can make rational decisions, sort of like having your will prepared.
Things you can do to help are having all of your medical information with you when you travel, as well as contact information for all of your doctors AND loved ones that need to be notified during an emergency.
I should add that if you have specific plans, like a living will, you should carry a copy of that with you so that your wishes are carried out in the event you are not able to explain them yourself.