I would definitely take a different airline, if I were as neurotic as you about the hand luggage policy......and leave TG to the rest of us who enjoy the airline and will usually take a small advantage of the carry on policy. I, for one, will take a single max size carry on, and a "large" laptop bag, and a rucksack, and this will do me for 7-10 days with hotel laundry helping out along the way.
THAI tends to offer Business Class for less money than all the other airlines you have quoted, especially from Japan, so ditch THAI and book with another airline.....PLEASE