That itinerary is crazy in coach for someone of your size. You seem like you have some financial means or at least some specialized skills (based upon your sentence that you have not flown < C in 10 years). You should cough up the money for Y+ or C. Really, your employer should pay for C. Perhaps you should negotiate this point with your employer or find a better employer.

Note: VS/SQ RTW in C is < $5,000. LAX-VS-LHR-VS-JNB-SQ-SIN-SQ-LAX.