Thanks for all the advice... the RTW option would have been nifty, but unfortunately cost is an issue (cheaper C fare is more easily justifiable to management). And neither BA nor SQ are on our approvied carrier list.

I'm leaning towards UA/LH outbound and LX inbound -- that way I get *A miles for the whole thing, and at least on one of the directions I get miles toward my Q4 CR1s. (I need to fly SFO-TLV-LAX, and so I'll ideally go SFO-FRA on UA, FRA-TLV on LH, and TLV-ZRH-LAX on LX.)