What do we have that was introduced after April, 1945? Certainly nothing British, Russian or Japanese. F4U-4 maybe?
I'm hard pressed to agree that the Germans are disadvantaged in AH any more than the Allies are by, due to clearly being about to win the war, not pushing their hotrods into combat.
From a game perspective, not a history perspective, I wish the IJN had not interfered with Jiro Horikoshi's A7M so that it could be in the game to help counter the dominance of late war American stuff over the Japanese, but twas not to be. The Navy insisted it use the same 1900hp engine that the N1K used, Horikoshi and Mitsubishi objected saying it would be underpowered, the Navy insisted and found the A7M1 to be unacceptable due to being underpowered and told Mitsubishi to redesign it to take the 2200hp engine Mitsubishi and Horikoshi had wanted to use in the first place. By the time the redesign was done there were B-29s bombing Japan and, if I recall, an earthquake also delayed things in 1945. End result, seven A7M2s built, none in service.
The F4U-4 is clearly the American example, and you are correct to point out that the allies didn't rush some things to the front that they would have had the war gone into 1946 (and that list is a big one). The allies would be looking at things like the -4, F7F, F8F, P80, Meteor, even hotter Spits, etc. All these would have been showing up in late 45 / early 46 at the front. I think what I am trying to get at is that the normal stream of new aircraft that would have been deployed by the Luftwaffe ended earlier than that, and really earlier than April 45.
Really for the Luftwaffe, go back to January '45 and in the aftermath of Operation Bodenplatte there wasn't much left. With pilots, fuel, and their airfields secure, the Luftwaffe would have been putting up more Me-262 variants, plus stuff like the He-162, the Do-335 (in limited numbers), better Ar-234 models, a 1.98 ata rated 109K using C3 fuel, etc. You are also correct to point out the Japanese had the same problem - military bureaucracy is universal.
From a game perspective would a perked Do-335 or A7M2 be that bad? Part of being a cartoon pilot is answering that what-if question. What if B-29s had to face Me-262s and Me163s? It cost perkies to find out, but it was fun.