I guess I am a bit confused as to why you would want 2 *G. You will have lounge access regradless, although ROP Platinum might get you into the First lounge in BKK (note: this is an assumption). Otherwise you will be splitting your points between programs and perhaps hurting yourself in that regard. I would check the *A redemption chart and compare it to the TG award chart to see if there is an advantage on crediting to ROP and SAS.

Why not consider one of the ME3 as well? Keep on *A (SK, TG) and then see if what you could get on Emirates or Qatar. If I were to push for elite on two programs, 2 different alliances would seem to make more sense in keeping future options open.