if I were you...I actually might consider getting comp to 1P on UA first (to get 100% bonus miles), and fly UA for these ? and with 3-4 trips to SIN a year, plus some leisure travel, you can get to 1K which would give you 6 SWU's the next year, which you can use to upgrade all the way to SIN (and if 6 = 3 roundtrips not enough, you can upgrade the rest with miles)? (I assume they won't comp to 1K).

and with UA, you have E+ which gives you a few more inches of pitch vs. CX there's no such thing...with Y these few inches might actually be quite important.

another option if you want to stick with AA, have you checked AA to SIN via NRT ? so USA-NRT on AA metal which you can upgrade with your VIPOW, and NRT-SIN a short flight in JL/AA-codeshare in Y (and I personally like JL Y more than CX Y - but it's the experience from a few years ago) - I think the food is nicer in JL Y and the pitch better. and JL gives the same 100% AAdv elite bonus, right ? if so I won't necessarily only stick with CX for Y...