It seems to me, that your play-group consist of conservative players ?
I’m curious how long your games take if everyone are playing “passive”…?
On topic note, i think this
Is 2 subs and 2 transports a decent buy for turn 1?
is, in my honest opinion, a horific buy. those two subs are absolutely useless until you get into war with uk/anzac/usa, and even then - Do you need more navy??? O.O Japan needs to concentrate on tasks at hand. The idea of convoying pac/anzac down is way too slow for my taste. (im a cow kinda guy - i want to jump the gun right away or slowest at J2).
Your J1 buy in my opinion should either be 2 TTs and minor IC, or 3 TTs and do whatever with your 5 IPC. I tend to save those for next turn to keep since you could use em for a tank on the newly build minor IC.
As for your transporters go, and i mentioned it earlier - doing this kinda slowplay, is still insanely valuable. So if you cannot defend your transports, that have a threat to be taken, all of them - then you cannot take the money islands in one go. Every time a TT dies down south, it has to come from Tokyo, or waste precious production of land units from mainland factories that might be closer.
As a follow up on taking the money islands, i would put alot into taking down calcutta and china. Even if calcutta is gonna cost you a plane or 5, get it for god sake. dont be a wanker ;)
Hope it helps somehow!
/Et