Top five most needed, no doubt should be devoted to the plane set with largest holes. Let's see.. our entire pre-1943 VVS set is missing, and Japanese mid/late war plane set has gaping holes.
Ok.. the agenda is:
1. The plane had to have seen at least somewhat significant service in WW2
2. It has to be basically competitive in the MA
3. It has to fill a reasonable role in the CT
4. You have to explain your choices.
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1. Ki-84-Ia(late JP)
Is the Spitfire and the N1K2 competitive? Heck, those two planes share combined kills of 20% in the MA! Then people are gonna love the Ki-84-Ia. Performance specs and maneuverability is simular to the Spitfire MkIX, and acceleration characteristics would be simular to a La-5FN. It is also the single missing "late war plane" amongst all countries(except Italy).
2. Yak-7A(early VVS)
Early war soviets used a mix of planes - among them are the Yaks. The early Yak choices available, would be the Yak-1 or the Yak-7 - the two-seat trainer Yaks were modified into a single-seat fighter to fill the shortage of Yak-1s. It would be pretty much limited in the MA, but a goode opponent among the early war planes - Bf109E-4, SpitMkIa, A6M2, C.202 and etc.
3. I-16/24(early VVS)
Another early war VVS plane. Alternative choice was the LaGG-3 - especially because the current plane set lacks most Lavochkin series fighters which saw use through out the whole war in the East. However, the popularity of the I-16 is immense among people who know them. It's funky shape, popularity, amazing maneuverability, plus the ability to carry rockets for variety of use, and scenario possibilities such as the Spanish Civil War, and usefulness in the CT, comes as a huge advantage over the LaGG.
4. Yak-1B(early/mid VVS)
The "first light" of Yak series fighters, which began to prove itself as an amazing competition to the Luftwaffe. Speed and climb characteristics a little short of the Bf109G-2, but maneuverability better than the F-4. It's historic role is significant, as the first real threat to the Luftwaffe, and it also provides a perfect mid-war plane for the VVS. Particularly useful in setups upto 1942. This mid-war plane evolves from the Yak-1 line.
5. Yak-9D(mid VVS)
The most numerously produced VVS fighter. It seems there are a lot of Yaks in VVS setups, but that is only natural. As many variants there are with all those 109s and 190s, the Yaks also evolved step-by-step to meet them. It's performance characteristics would be simular to our Yak-9T, but armed with the better performing ShVAK 20mm cannons.
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The Yak-9D could also be somewhat 'modified' from what we already have. Basically, just as late Bf109s have an option to mount either 20mm or 30mm cannons, we could offer the same choice to the Yak-9T. If it flies with the 20mms, it'd be a Yak-9D, and if it flies with a 37mm, it becomes a Yak-9T.
So, if in that case, the Yak-9D, is "incorporated" into the existing plane set as described above, then the alternative fifth choice for me would be:
5. P-39N
Large quantities of the P-39s have been lend-leased to the Soviet Union. It's specs are little lacking compared to mid-war Bf109s such as the G-2, but it has a potential of becoming a very characteristic and competitive plane. Another plus side is, this plane belongs to a US plane set, but also has significant meaning to the VVS plane set - most of all VVS aces have been born from the P-39 - Glinka brothers, Fadeyev, Pokryshkin, you name it.
Additionally welcome, would be the Ki-43, Ki-44, Ki-45,
A6M3, Mig-3, LaGG-3, P-38G.