Since these trips will most likely be on UA metal (SQ may be servicing these routes at a later date), you should consider UA MP. You'd easily reach 1K status, collect many RDMs and get 6 systemwide upgrades per year, which you can use on both UA and LH metal to get from Y to C or from C to F. Actually, with your travel pattern, it might be possible to make both UA 1K and LH SEN, because LH SEN has to be renewed only every other year. So, just like me, you could have both.

UA will probably match your QF Platinum with Premiere Executive (1P). That would give your *A miles an easy start, as you'd have *G status (= worldwide lounge access except USA) right from the beginning AND get a 100% mileage bonus on UA metal (and all LH transatlantic flights).