Well as we have kept a strong infantry backbone branching out to paratroops wouldn't be that far off. The downside is that Japan doesn't really have all that many good opportunities to use paratroops, since for the most part its too risky to use paratroops against large infantry heavy armies and when used in tactical operations such as a pacific blitzkrieg the lack of proximity to an airbase, makes them in general a 'one or two shot use weapon', which is about the same as using sea transports and normal (better) divisions.
Thus said the paratrooper option isn't that useful.
Having said that, I have used them in the past rather well in Siberia, and in Burma. In the first sense, basically it was to cut off the TSR and encircle the entire Russian army via a general OOS and disruptive effect. If your going full hog against the Russians, this is the best you can do, however even then using cavalry into Mongolia and the heart of steps is still the long term better option, but its harder in Manchuria. In Burma you can 'cut the retreats' by encircling places like Rangoon or dropping into the hills and mountains screwing up the Allies against your forces there allowing several pockets.
However given we aren't fighting in either these places, tactically there ain't much use here for having them. Strategically it leaves it open, but with the war in China a stalemate our strategic options need to be focused there in my opinion.
If/when China is taken, I will be lobbying for a strategic spread of our war assets, mainly to provide us with an offset via the Soviets, because although an early Allied intervention is more likely, I don't see an easy way that we could 'win' the war in the pacific, that would end up being a drain on our resources. Also if we do 'peace out' with the US, they are more than likely to join the Allies. At which point further Pacific gains are really closed to us*. At this point the late game would become focused on the 'Soviet threat', and if we or them act on this.
Given the event system in HPP and the way that the Eastern front in my opinion appears to end up being a Russian win, I think a late soviet stab is fairly likely, and it can also be disastrous if the Soviets get their momentum going.
*Not that it matters. I mean we've not earnt a lot of Cybvep's VPs in the pacific, but if this was put in a historical context, Japan has shown that she can take on one of the major world powers in the USA and come away with the Philippines. This would very much internationally establish Japan as a Great Power in the post WWII setting to stand alongside the Allies against communism. And so maybe not a 'war goal victory' it would certainly be a Japanese victory to get to where she has wanted to be since the 1850s.
Assuming that the Military is brought to sense following the wars, then that would very much set up Japan as a world superpower within a few decades as China would be industrialised, and providing the 'consumer market' for American style free trade, and outsourcing of labour. In essence you’d get Chinas current modernisation almost 40 years earlier than historically.
Remember that Anglo-Japanese relations were generally good in the period before the war, and since we never declared Pearl Harbour, technically we are still the 'good guys' especially if we haven't joined in with Hitler and Mussolini. While Churchill in this timeline would no doubt be suspicious of us, we would still likely be on better terms with Britain, than Britain was with Stalin at this time.
Whether or not the game agrees that's a different point, since it is inherently designed to antagonise each other into war, irrespective of what Japan or Britain does in game. Indeed if America had taken its declaration of war like it did, Britain and Americas relationship would be icy, if not frozen! Since the whole point of keeping Japan 'cosy' was to protect British interests in the region, like during the Great War. In this time line America is very much threatening British interests with 'imperialistic attitudes', even if not directly with ideological clashes. After all, the 'Allies' are not a monolithic entity, each had/has their own reservations with each other.
As points of note, we should probably have a leader present at the Tehran Conference in late '43, and then also be present in the Yalta Conference '45 even if we're not in the war against Hitler, we are still 'in the war' so to speak, and no doubt will want to secure Japans continued 'non-aggression', or even aggression! with the 3rd Reich.
If this was an AH, that may also set the date and time for Japans exit of both wars, with the Americans giving a peace with Japan given some of her taken holdings, in return for a peace in China. Historically Japan wouldn't have accepted this based on historic precedent, but given there are differences in leadership, given that their are differences in the naval results, a more 'forgiving American position' could leave an acceptable treaty on China on the table. Indeed a Balkanised China is in everybody, but the nationalists, favour...
If I was running the AAR, then I might forward a treaty from the American position along those lines. However it ends us being Cybveps prerogative here, so I don't know how things are going to play out Politically. I waffle on too much...