Mauritus is a not as strong a winner for DONEx tickets than it is for a AONEx - especially with recent exchange rate changes. The OP could mention which 4 continents, and ideally which cities, he will travel to. Needing to add a continent would add to the cost and hassle. Likewise adding a separate flight. E.g. I don't believe going out of your way to get to MRU would make sense if you already planned to go to South Africa.