It sounds like I missed the chapter where you've decided to fly MRU-JNB-HKG etc. Cathay might indeed be willing to ticket that. If you have a toll-free number for them, it's easy enough to ask. Many of us have enjoyed excellent booking services out of CMB; they respond quickly and intelligently to email, and may be able to tell you whether or not they'd do it. You'll also need a way to pay for the tickets in Mauritius, i.e. a GSA, so ask Cathay about that as well. I suppose IBL Travel will do that for you but I've only asked about BA. PM for the Cathay email contact.

[Aside: It being December, have ex-MRU prices gone up, or are they still the same?]