The floatplane N1K was a substantially different aircraft to our N1K-2 and couldn't be done as a variant.
The Ju 188 wouldn't really work as a variant either, it would need new cockpit art for starters. The Ju 88A-5 would be easier to model than the A-1 as a BoB variant. The A-5 was essentially an A-1 but with the A-4's extended outer wing panels.
IIRC I did suggest to HTC that they add the earlier armament options to the remodelled Ki-61 as hangar loadouts, like they did with the Hurri IIA/B/C. Not sure why they didn't go for this, it would have been handy for New Guinea scenarios.
The Me-109E-1 could probably be added as a hangar loadout to the existing or a future remodelled aircraft as well.
Thought of another good variant. The F4F-3:- great for early Pacific scenarios, less guns but a lot lighter than the F4F-4.