Interesting problem and tradeoffs to be made. So let us know what you finally go with.
Now here’s your challenge. The easiest and generally best place for redemption is generally any US airline (because of low/no YQ and generally low mileage requirements) - so from a pure redemption perspective I’d go with AA on OW.
The problem with doing that is 3 fold - BA credits miserly to AA and other programs - you can earn upto 250%-350% RDM on BA J. You earn about 125% on AA, CX etc. So half or less. The second problem is that Citi doesn’t transfer to AA. And finally you get screwed on the lounge access while traveling domestic in the US.
I wouldn’t credit to BA because while the earnings there are double or more... redemptions with them require significantly more miles - but not double. But then they have the dreaded YQ! And with BA it’s quite a lot of money.
The options then are CX, QR and QF.
I’d go with CX. Very decent redemption charts. Great airlines to fly with. And generally better award availablility for their own members as you’re only looking at SE Asia redemptions.
I have a more difficult question for you. Why BA in J?
Even to get to some of the smaller cities in the US I’d prefer LH, LX, TK or even EY, EK, QR doing a 2 stop.