Just go with AA and OW.
Redeeming on SQ for premium cabins is pretty much impossible for non-SQ Krisflyer members. There have been cases where SEN/HON status members of M&M have been able to redeem in SQ J/F...
If you want better premium cabin awards and more airlines, *A is the way to go. You have the new LH F and great choices in OZ F/C, NH F/C, LX F/C, SQ F/C, TG F/C, etc.