Thanks for all the suggestions. I'm still thinking through what to do here. Some immediate responses --

I do know about the 1 Jul rule change allowing AA mileage earning for BA flights other than those to/from the US. But I have to travel before then. Next time!

benoit, I know that the RTW rules say the US and Canada are one country for the purpose of RTW rules. It was with that in mind that I thought I'd have a problem, under the one-international-arrival/departure-to-country-of-origin clause, if I went to the Caribbean. No? Seems like we rarely see Caribbean routings on NA-originating RTWs, but maybe I just haven't been noticing / paying attention.

I like the DFW-ANC-DFW suggestion. Quite a mileage run. Will think about it.

The AMS-HKG tip is a great one. I thought about this, but my schedule is such that AMS probably has to be at the start of my Europe travels rather than the end. Otherwise I'd definitely do it and save a European segment that way.

headinclouds, as to Bali, that looks ilke quite a great place for a stop. More character, someplace I've never been before and might not get to otherwise, and of course far cheaper than NRT. But it has only two-class service from HKG, not three. I don't mind CX's regional business class, but 2000+ miles is more of it than I'd like, especially when I'm paying the higher fare for the A ticket rather than D. I don't suppose there's any destination that's both as desirable as Bali (along the axes sketched above) and also served by a three-class plane? Picky picky, I know!...

Thanks again, folks. It's such a pleasure to have this group to consult.