Jason Williams of 777/1C Studios has stated several times he would love to do an updated Pacific Theater add on to the current Great Battles series, but they are greatly hampered by a lack of detailed data on the Japanese planes. There's a fair amount of info on the flight model of the Zero, but very little data on other planes of the Imperial Japanese navy and to dig into the archives to find what little there might be obviously requires a knowledge of Japanese. The short term solution was to simply skip that theater of the war and just keep putting out Eastern and Western front add ons until they, hopefully, got more info.
I don't buy the "no data" excuse as being insurmountable. With current technology it should not be a huge problem to extrapolate performance data given known aircraft dimensions, weight, power etc. At least good enough for a sim.
Besides, I'm not one of those who requires that every single thing about every facet of an aircraft has to be modeled to absolute perfection. This trend toward "if we don't have a 3 feet high stack of flight test / systems documentation we're just not going to make it" attitude is going to leave a bunch of HUGE gapping holes in the flight sim fleet.
I'd rather have a "close enough" representation of such aircraft than none at all. I seem to recall the relative flight performance (IE how the airspeed, turn rates etc compared relative to one another) of Wildcats, Hellcats, Corsairs, Zeroes, P-40's, Vals, Georges, Franks, Tonys, Kates, SBD's etc. to be pretty good back in the old "1942 Pacific Air War" days.
Besides, if they get the Kate's performance specs off by 5% who is going to know? It's not like there are a bunch of old Kate pilots around who are going to call them on it.