I tried to ticket this sort of routing again about a year ago, and absolutely no luck. I don't think it's possible any longer.

There certainly are other carriers that would let you do this sort of routing, I earn BMI miles for this reason, they tend to be pretty flexible on routing and I suspect this would pass muster with them. US-South America-Africa really isnt pushing it, realistically it's not much more flying than going thru northern europe.