With the addition of MAD-JNB and HKG-MAD I'd look into a DONE4 with:
JNB-MAD-DOH-GRU-USA-ASIA-HKG-EU-DOH-CPT for maximum mileage.
Would I be able to keep both connections in each EU and DOH? Only the 2nd EU visit would be a stopover. Neither stop in DOH is over 24hr.