I recently bought a similar fare (with an overnight layover in HKG). I just bought it off the CX website without even realizing there was a layover. I ran a fare search and clicked the first or second available routing from their list and bought it.

I'm an MPO SL also. I called everyone I could think of and begged and they refused to cover it as an STPC. I'd like to hear it if anyone has any tips on this.

I ended up paying for a night at the Regal airport hotel, it wasn't bad at all.