The problem, as I understand it, is the conflict between (1)following corporate policy (sit in Y for one specific flight) and (2)trying to be a good corporate citizen (spending the least amount of money while following travel policies).

In my experience, the people who need to approve expense reports -- the mid-level and senior managers and the people in accounting/finance departments -- are going to have no familiarity or understanding of RTW ticket benefits. They want to know that policies have been followed, and if so, then all is ok.

So, as long as you can turn in a ticket receipt (not BP, but ticket receipt) that shows economy class HKG-ORD and business class for other international segments, you would be OK. AlB's suggestion (buy a Y RTW, then upgrade to a C RTW) would be the easiest for the people traveling, though it could be problematic if tickets have to be purchased/written by your corporate travel group.