[The A6M as a fighter design of 1940 was on a par with or superior to most other designs of the time, including the first versions of the 109 and Spit. Like the F4F itself, all started off unarmored and armed largely with MG's. Even the FW190 (the very first varient) was initially armed with IIRC four MG's but was quickly upgraded with cannon to combat the heavy aircraft it was facing. So i would strongly disagree if by "beginning of the war" you mean WWII in general. Even by late 41 the Zero still was a formidable design. I don't fall in with the typical discounts of the planes success anymore than with the pilots who flew it. Any side can be discounted. I participated in an intersting what if thread that asked about a possible alternate outcome to the BoB if you swapped it with another plane. My choice was the A6M. It was the world's first strategic fighter. It had the range that the 109 lacked. The 109 may have been more upgradable and could have armor installed, but without the range all it's other attributes were useless because it couldn't be where it was needed nor linger long enough to be effective. Was the 109 flawed? No. Its attributes simply did not account for strategic range when it was designed nor were drop tanks part of it's design from the get go.
there were no tradeoffs per se for it being a carrier fighter. In fact it was the A6M that proved that a carrier fighter by default had to be inferior of flawed compared to a land based fighter. Later fighter designs like the F4U and F6F would further prove that. However the A6M design was tight, meaning it could not be readily improved or expanded upon. This tightness wasn't due to 'flaws' but due to the state of the Japanese aircraft industry which limited the total HP it's engine(s) could generate. Thus, the A6M could not be adequately upgraded over time, as were the Spit, Hurricane, 109 and F4F with self sealing tanks and pilot armor. The A6M design revolved around the 950hp Sakai engine and it's specifications were driven by that barrier, thus to meet all of it's specifications it had to be as light as possible with no wiggle room. More powerful engines allowed some upgrading but not enough to keep the plane competetive. However the Reisen's builder himself stated from the beginning that a good fighter design on average has a shelf life of 2-3 years then must be replaced by the next generation. Again Japan's aircraft industry was not up to the task. They couldn't even build enough Zeros much less deploy it's successor....the least worst course of action was to keep building an obsolete plane. As Jiro put it...."better to have an obsolete fighter in the air vs. no fighter in the air" This isn't a flaw in the A6M itself. In it's prime (40-42) it's outstanding combination of speed, agility and hitting power made it a dangerous and competetive foe. Weaknesses? of course. I am unaware of any plane that didn't have them. But "Flawed" is to me a grossly inaccurate term to use.
Ki-43 was by 1942, more obsolecent in concept, something Nakajama realized which was why they steered towards the Ki-61 and 84 but it was not flawed either. More so than the A6M it was built to dogfight, something the army pilots were used too from their Ki-27 days. Initial production models had teething issues but once resolved the plane served well. The definitive Ki-43II version was a dangerous opponent but underarmed when asked to intercept the increasing numbers of heavily armored bombers. This didn't stop it from scoring success however. It stymied the RAF Hurricanes and scored competetively against even later 2nd generation aircraft including the Spitfire VIII. In Burma the JAAF was only defeated ultimately by sheer numbers and lack of support/reinforcement. It can be deemed a "failure" as an interceptor but it was never designed to be one anymore than the Ki-44 was designed to be a dogfighter. Often forgotten is that the Ki-43 shares a good portion of the success of Japan's initial thrusts....being misidentified as a Type 0 or "Zero"
something that continues to occur to this day in modern literature. The Ki-43 gets no street credit. Yet more JAAF pilots became aces in it than any other type.
Nice dissertation, and one that I largely agree with. In particular the Sakai engine stuck at 950hp. This to me was Japan's biggest undoing: inability to upgrade the power of their engine designs from 42 - 43. They got them working in mid 44, but by then they were already several steps behind in HP. And like it or not, HP/lb engine weight is what drives fighter designs more than anything else. Losing those two years was crucial ....