However looking at what you wrote: Crediting to MPC would be of much less value for you in terms of award miles: Does losing 1/2 of the possible award miles sound good to you in exchange for a bottle of water for that 1 flight you might take in economy on CX?
Don't mean to go OT on my own thread here, but, and this is pure speculation on my part, I don't think the AS 70K CX F with a stopover redemption is going to last indefinitely. I mean, for instance, CX F HND - HKG - JFK for 70K? On general principle, one would have to redeem this, in my view. So, the risk is earning tons of AS currency, and be subject to devaluation, especially since domestic redemptions have little or no value for me.
Generally, when I sense change, I don't wait around, try to be amongst the first out the door, and never bother sticking around for the hindsight analysis. Since MPC has recently devalued (at least from what I read), I'm assuming it'll be safe from further devaluation, at least for several years? So, perhaps, this may be a prudent time to hedge with DM & leveraging AM for future potential redemptions.
Of course, not having extensive experience with MPC, all of my paper theorist stuff may be completely off base, like my...er...idea on the SIN-HKG-TYO detour. Really glad I asked before implementing that plan, which initially, at least to me, seemed somewhat plausible.
PS - Also, with the recent mistake fare thing, I'm assuming any HKG - JFK redemptions will be unavailable to partners, hence, my reluctance to earn tons of AS miles to "save" for next year. Unless it's Amex MR, I like to earn and burn asap.