I booked a CX flight for January using my JL Sapphire number, thinking I will get to choose seats and get into lounge (since I am back down to lowly Green in MPC). I just recently realized that I am about 150 Asia Miles short of a redemption target to use up my Asia Miles before expiration in February. Can I switch the FF# for my flight to MPC to get the miles required after I choose the seats and get a lounge pass? Or better just let my wife invite me into lounges (she is also JL Sapphire)? Or actually easier to buy those required miles?

Thanks.