I have experimented with going after Japan in several recent games. Although I still consider my startegy far from perfect – Pacific is really messy! – I think Japan can be really squeezed into corner quite easily, but there has to be one condition met. And this is at least one of the battles does not go for the Japan well.
If Japan fails Pearl or does it heavy and loses some ships, or has very light presence in China or – most often – exposes some of its ships to counters, there are two stretegies you can really follow with success: 1. US IC build on Sink R1 and UK IC build on India R2 plus naval buys US or 2. just naval buys US which is the way to go if Japan lost or is about to lose 2 of its capital ships.
If Japan does not make mistakes R1 and does not hit bad luck though, I think it is very difficult to break it. But then still you can slow it most of the times sufficiently to get to Berlin the same round japs get to mosc which should be sufficient.
Japan definitely does not need to be house ruled to weaken them.