Given that you put lounge access as the most important FFP factor then you'll obviously be aiming for *G. It's going to be virtually impossible to get that in LO/LH if you're flying mostly Y so your best option might be something like A3 (with judicious use of SK flights) or SK itself. With your mileage it should be within reach to attain *G using those programs. Obviously, A3 is much easier to maintain once you've achieved it.