Hi Shed
They surely couldn't expand T3 whilst the TP work on T2 is being undertaken. I suspect they would also need some more car parking space.
Re Cathay - it is probably a combination of being surprised at the sucess of the route (unsure whether to use the B77W or A359) grabbing slots at Gatwick and crew/staff problems.
I hope SQ copy the CX model when/if they delink from MUC.