Hm.

Might I ask how you're getting to and from Japan? Also, what other major travel plans do you have for 2015?

The reason being, given this thread is about tier points and business-class travel options, I wonder if there might be a fit with one of Oneworld's RTW or multi-continent products.

Without getting overly complicated in this thread (there are sticky threads on this board where you can study these products in depth) suffice to say that RTWs and related tickets are priced very differently depending on the country of origin. For example, a three-continent business class RTW ticket originating in the UK (or the Euro zone, pretty similar) is priced at £5471 (plus taxes and fees.) The same ticket bought in Japan is £3767. Both would give you up to sixteen business-class flights (US domestic first class on routes without J) and is good for a year.

So, one (of many) scenarios might be for you to travel to Japan on your existing ticket, then instead of returning home via Asia, buy an RTW ticket there and return via North America, maybe with a short TP run there, given the great potential for massive tier point accumulation using the first-class TPs you'd get on domestic AA flights. Then home across the Atlantic.

Then, later, off you go to China, with or without a stop in the Middle East (or anywhere in Europe, or both) en route, do your Chengdu/Hong Kong thing, then just carry on back to Japan to end the RTW. Use the return portion of your prior outbound Japan ticket to get home.

On a benefit/cost basis, and depending on how eager you are to accumulate TPs, this might be a reasonable way to go, and if you have time, it could also be a great way to visit some places or try different airlines, that you'd otherwise be unable to experience.

Just a thought - I'm always looking for ways to leverage airfare into greater benefit, or to create new travel options.