Ki-116 would be interesting, less power but IIRC they also managed to cut down weight.
Of those only the nitrous oxide injection and R models could be added unfortunately. Though a Ha-44 Ki-84 would be really good, it’s the engine we have right now in the Ki-83.
From the mentioned “Japanese Secret Projects” by Edwin M. Dyer III :
" …nor the Japanese version of the He 162 would progress past the initial design stage. Only the Nakajima Ki-201 ever made it to the construction phase which, by the end of the war, amounted to a single incomplete fuselage.
As a note, ‘Ki-162’ has been used by some as the designation for the Japanese produced He 162.
There is no historical evidence to sup-port this although it is not without precedent, such as the case with the proposed Mitsubishi Ki-90 that was to be the Japanese version of the Junkers Ju 90."
It could also be confusion with similar designs such as the Baika.
I find the later Japanese 18-cylinder radials extremely interesting. For most of the war, Japanese engines lagged somewhat behind other nations, but they managed to really supercharge their efforts (pun intended) and produce the Ha-43 and Homare. The Homare is very impressive given how much power its later models produced within such a small frame. The Ha-43 is probably my favorite Japanese engine, but the Ha-42 is cool too. I believe it was to be used on the Ki-91 as well.
I believe there was a 3000 hp radial planned as well
3100hp radial would be the 22-cylinder Mitsubishi Ha-50. It had 2 rows of 11 cylinders, which made the diameter much larger. At least one document lists it for Ki-91.
Other over 3000hp engines include 3400hp Aichi Ha-70. Rather well known 24-cylinder twinned V-engine for R2Y1.
There was also the 5000hp 36-cylinder 4-row Nakajima Ha-54 for gigantic bombers. Quite a long documentation of this engine has survived.
Would be nice to see the A7M3-J Kai get added to the game,
A7M3-J Reppū-Kai
land-based interceptor version powered by a 2,200 hp (1,600 kW) turbo-supercharged Mitsubishi Ha-43 engine including an inter-cooler, with a maximum speed of 648 km/h (402 mph). The armament consisted of six 30 mm (1.20 in) Type 5 autocannon, four wing-mounted & two oblique fuselage-mounted.
with that payload, fighting airtargets would be fun