I simply rerouted my itinerary with the AA ATW desk which organised my itinerary in the first place - even when the bits I wanted to reroute weren't AA segments. I was allowed to hold the new flights without reissuing for as long as I wanted (these include QF, CX and JL segments), and I only did the reissuing when I arrived at NRT where I started my ticket; I think this could be because my itinerary was no longer eticketable.

BTW no $125 fee if reissued before departure if you're originating from TC2/3. Whether the tariffs desk you're dealing with knows this rule or not is another story... I had to make a few calls to AA NRT before I got someone who knew what he was doing and removed the fee. I think the US tariffs desk also makes this mistake quite a bit.