The floatplane version of the N1K, the "Rex", was a high-performance aircraft that gave all but the top-end Allied fighters fits.
The float did impair performance, but in a desperate situation, the float could be jettisoned, and the Rex (floatless) became an extremely dangerous aircraft, since it no longer had the weight and drag of the float, or the weight of the internal landing gear mechanisms. Thus, it became a lightweight fighter with extreme maneuverablity, capable of dealing with a Corsair, F6F, or P-51 on more than equal terms. The drawback is, of course, that you have to belly it in somewhere if you manage to survive the encounter.
This is what prompted the IJN to convert the aircraft into a true fighter design. The N1K1 and N1K2 (low wing and mid-wing Nikis) were both not as maneuverable as the floatless Rex because of the added weight of the landing gear, but were still formidable fighters.
The Rufe was not as lucky. Yes, it was used in combat, and it could turn as well as a Zero at lower speeds. It was heavier, had higher wing loading, and was slower than the A6M, but it could still hold it's own against F4Fs. In fact, performance of the two was actually pretty evenly matched.
I think that a PBY, Piper Cub/L-4, Dornier Do-24, Storch or other a/c of that type in-game would be great, not only for flying in supplies, but having the ability to fly out and pick up a ditched pilot, bringing him home and allowing him to land his kills.
J