1) Although far rarer than the Ki-44, I believe you IJAAF fans would be quite impressed with the Ki-100 (only 384 built). Although the validity of combat accounts is questionable (a matter of "we said/they said"), the plane was highly regarded by Japanese pilots. Supposedly it could dive with pony's and not worry about shedding parts or energy. It was also described as having superior maneuverability to the F6F.
The KI-100 wasn't that a great improvement over the KI-61 model we have now. Each had it's trade-offs - the KI-61 was faster but the KI-100 could climb better and had a higher ceiling.
Performance:Maximum Speed (Ki-61-I): 348 mph (560 km/h)
Maximum Speed (Ki-61-II): 379 mph (610 km/h)
Maximum Speed (Ki-100): 367 mph (590 km/h)
Initial climb (Ki-61): 2,200 ft./min (675 m/min)
Initial climb (Ki-100): 3,280 ft./min (1000 m/min)
Service Ceiling (Ki-61-I): 32,800 ft. (10,000m)
Service Ceiling (Ki-61-II): 36,089 ft. (11,000m)
Service Ceiling (Ki-100): 37,729 ft. (11,500m)
Range (Ki-61): 990-1,100 Miles (1600-1800 km)
Range (Ki-100): 1,243 Miles (2000 km)
The KI-100's main advantage was the better reliability and
MAINLY the availability of the Mitsubishi Ha-112 II radial engine which replaced the Kawasaki Ha-140 inline engine of the KI-61 - the production of which was destroyed by B-29 raids on the factory. (A problem not delt with here in AH2).

Also, my sources say only 275 pre-built KI-61's were converted to the KI-100 standard.
The KI-100 was not a new built plane - but already built KI-61's that had the Ha-112-II radial engine fitted. It had all the structural problems inherant from the KI-61. Though it was slower, it did prove more manuverable and quicker to cimb as you stated.
MAIN QUESTION it is going to come down to, is do we need another late war Japanese plane when we got the N1K2 GEORGE & KI-84 FRANK or do we need another fighter for the mid to late period like the KI-44 TOJO. Would like to have them all but you only get them one at a time.

<S>!