Also the north African destinations you mentioned are all included as part of Europe for OWE itineraries. All service to those destinations is via other European gateways, typically one of the Spanish or London airports.

The OWE does allow surface segments, and although the rules prohibit transoceanic (Atlantic/Pacific) surface travel, I don't think it would rule out intercontinental surface travel between Europe and Asia. If memory serves, a recent itinerary posted here had someone going HKG-BKK/DXB-LHR or some such, so if you wanted to take the train I think you could do it. You would then be able to use any remaining flight coupons for intra-Asia or other travel, provided you observed all the other rules.

You might also have a look at the OW Global Explorer product as well as Star Alliance's RTW offerings. Those are mileage-based but allow for slightly more flexibility in route planning, and you can go from S. America to S. Africa directly on Varig (*A) but not SWP-S. America as you can with OW. (Intra-Africa is still a weak link in all RTW programs IMO.) The OWE is more flexible in general.