Well, Eddie, if you can’t wait for FMG’s rollout (which looks like it’s going to blow the doors off anything I’ve seen yet, short of a very expensive set built up from metal miniatures), you might find much of what you’re looking for by trying the following:
1. Table Tactics’s line-up (Specifically their “Central Powers” & “Axis & Allies Accessories” sets)
2. The piece set from The War Game, which could be purchased separately from the game itself last I checked out their website
3. For infantry variants, there are numerous HO-scale minis you could buy off the shelf.
If you want a more detailed breakdown, I could give you some…
But if you can wait, I think FMG’s stuff will be new standard for quality and give you at least 90% of what you want, at least.
Oh, by the way: the Japanese never fielded anything close to a “pocket battleship.”