Definitely not boring... I usually read most of the stuff posted if I find it to be interesting. After all it makes it easier to answer if you provide more information.
From the info you just gave, it seems like you value the award miles much more than the status. So based on this I'd say that you should definitely fly JAL direct SIN-TYO and credit to JAL just like Kaka already suggested. Honestly speaking status doesn't matter that much anyways if you mostly fly J/F for work. Sure, its nice to have lounge access and all that for your personal trips but lets be realistic, how often does one fly for personal reasons anyways... and when you do fly for personal reasons and you redeem F/J it also doesn't really matter what status you have. Except for those little things, you get the same stuff when flying premium cabins as if you'd have some sort of status.
I'm just trying to figure out how to maximize my rebate over the next 12 months, and whether or not DM is worth, say, forgoing the miles I can earn on AS or, now, thanks to Kaka, JL. But, if it's DM, I'd have to credit to MPC immediately to even have a shot at it this year.
If it was me, I'd probably go for DM, but I also fly a lot more in economy so its a completely different case. if you fly in longhauls in PEY or Y you really might value the difference of service, lounges, luggage allowance etc. . However looking at what you wrote:
So, I'd fly there once or twice a year and used AA miles to redeem CX F. Then, after AA devaluation, CX F price when from 70k(?) to 120K, I changed to AS, which has kept CX F at 70K, and with a stopover.
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?