The problem you aren’t seeing is that Japan can easily put 2 subs off borneo, a fleet off of Malaya, and a fleet off of East Indies so that UK will get convoyed for most of her money. Japan still would be able to get Kwangtung, and set up for a take of all 4 Islands and Malaya turn 3. A good Japan player should have one transport in sea zone 20 that could take Borneo or Malaya on turn 2 anyways.
You’re forgetting that UK is not at war with Japan on it’s turn. Japan won’t get any convoy disruptions, but neither do the UK get any NO money. ANZAC will, though. Unless you’re talking about the next turn, when Japan should be declaring war regardless.
We had this happen to us once in a game. We were more than happy to leave the US alone and crush the British. It delays the takeover of the DEI for a turn, but it’s worth not having to deal with the US until at least Turn 4.
The problem for the allies is not how to harass Japan, but how to hold the victory cities long enough to take Germany down. Not sure this is very effective to that end. Pain in the behind does not equal victory.