According to
Trans Maldivian you'll need your multi engine rating as you've pointed out.
Friends have flown for them, they had extensive Twin Otter and float time before they went over.
It is fun but if your goal is airlines then you'd only want to do it for a couple of years before moving on.
Usually operations like this the pilots do a lot more than just fly the aircraft. They'll be briefing the pax, assisting with loading the bags and catering and washing the aircraft.