It is a time consuming process to combine the places you want to see and the restrictions of these tickets.
I did several RTWs on OW in the past, currently most of my RTW travel is on Star.
The general strategy I am using is:
Let the RTW do the 'heavy lifting', e.g. all the long sectors or going to places where regular tickets are expensive (Easter Island for example). This will consume your 16 tcoupon limit. Avoid surface sectors, since the 16 limit is your most severe restriction.
Then look where you can buy extra tickets. Focus do do this in places where you can get in/out on your Star or OW RTW.
In Africa you typically find good fares JNB (do Victoria Falls etc from there).
In Asia BKK is a good place. Many options and inexpensive flights from there - this could cover Vietnam, Cambodia, Laos. On Star it is easy to do Europe-India-China-BKK-Australia. On OW you likely would make HKG into your Hub and do Europe-India-HKG and then sidetrips to China, Vietnam (UA has good fares HKG-SGN) and continue to Australia. Bali should be a bit more expensive then the other places, so include this into the RTW (from BKK, SIN on Star, HKG form OW).
Flights inside Australia are not too expensive. If you do a Star RTW you can either fly into one place and then buy a chain of OW tickets there or do a surface sector (will eat up one coupon) unless somebody comes up with a better idea. Easier on a OW RTW, since Qantas is OW.
If you move your starting point to JNB you should plan to go Africa-Asia-Australia-South America-America-Europe (stop) and then use the remaining ticket for a second vacation in South Africa (and use the return from your original positioning flight to get back from there).
NRT or ICN are also good starting points. Position there. Then do Asia - Africa - Europe - North Am - South AM - Australia - Asia (or the other way around).
On the Star tickets you can transition one continent more then once. The restriction is that you need and can do only exactly one flight between the 3 regions on this planet (Europe/Africa / N+S America / Asia+Australia). This makes it easier because you can do Europe-Africa(JNB)-Europe or NorthAm-SouthAM-NorthAm. But here you pay for the mileage (and these itineraries eat up a lot of miles).