I would book CI E+ for $1000 just because the timing is the best. Transit via TPE also seamless.

OP mentioned flying JL Business on this trip will guarantee re-qualify with AA Gold. That's $700 over the CI fare for a low level status. OP is AA Platinum now so there is a good chance he will get a soft-landing to Gold automatically if he didn't re-qualify for Platinum. Additionally, AA usually offers existing Gold a cash option ($400 or something like that) to retain Gold status if one just miss re-qualification. My gut reaction is $700 is good investment if it guarantees Platinum for next year but poor investment if it only guarantees Gold, considering there may be a soft-landing anyway.

Edit: Looks like AA did away with soft landing last year... so OP will not get bump down to Gold. So maybe it is worth the extra $ to ensure re-qualification.