I am in a similar dilemma, have been loyal to BA for years, have lots of BA miles, currently BA Gold and have now been based in Singapore for nearly a year. I am not quite sure yet how much longer I will stay here (could be anything between 2 and 24 more months, most likely 12+ though - the joys of Consulting

). Flights back to London and other company travel is usually J. So far I have traveled BA and Oneworld where possible, otherwise (typically short haul, holidays) will often be SQ from here where I have no status.
I have stuck with BA / oneworld for now on my longhaul J flights to maintain status with BA. I think getting status with SQ would be more difficult and take time, and given I don't know how long I will be here I may not get to 'reap' the benefits. I am very tempted though to use SQ J on one of my London flights...
That said though, it has been painful seeing one 241 already expire, with another one to go shortly
So what should I do?