I have a few suggestions, if I may. I think your work here is simply brilliant and very well done. It is such a top shelf mod. I really love that you've included a lot without making things wildly overcomplex. You've created choices for the player where there weren't really any before, without getting way too far into the weeds. Now there is a choice on what type of tanks I want, or how I need to build my air force; and there is now a real choice between converting production lines to a new model or continuing with the older model. This is far and away my favorite mod of the tech tree.

I think the carrier deck armor that is currently in the slot with the AA guns, should be in the slot with the third hangar space. Historically, that was a significant choice between deck armor and plane capacity, and is the reason why British carriers had a much smaller compliment than US carriers. Moving this over would also give the US carriers more historically realistic speeds. As of right now, the US Lexington class carriers have sub-30 knot speeds, when they were really capable of more than 33 knots. This historical speed difference is why Ranger and Wasp were kept in the Atlantic, but the Lexingtons and Yorktowns were utilized in the Pacific. Related to that, Wasp was a near copy of the Yorktowns, but with less capable machinery in order to meet treaty restrictions, so is a good reference point to set the treaty limitations at in game (in real life, the limitations on carriers worked differently than the game, but still, that's the best way to make it work). Same with North Carolina and South Dakota classes being at the limit for treaty battleships, and Iowas at the limit of the escalator clause.

The Ranger ought to be a early carrier instead of a BB conversion. She was the first purpose-built US carrier.

For the US Night Fighter II, you could use the P-38M Night Lightning. And for the US Torpedo Bomber V, you could move the TBM-3 Avenger up one and then use the TBY Sea Wolf at Torpedo Bomber VI.

And the US air group lists could be overhauled. The Navy/Marine Corps squadrons should be in the format of VF-2 or VMSB-241. You could change the 'CAS equipment' names to Fighter-Bomber Group, as that was the case with all single-engine bomber units in the USAAF after 1943. The other bombardment squadrons could have parenthetical notations added to indicate what type of equipment they had. I.e. "3rd Bombardment Group (Light)". This was done historically, and you could separate the Light, Tactical, Strategic, and Heavy Strategic Bombers with (Light) (Medium) (Heavy) and (Very Heavy). The British squadrons also fit into some patterns as well.

Another thought I had that is a bit out of left field, but worth considering, would be to make light carriers a subvariant of cruisers rather than carriers. This really could go either way, since historically, US Light Carriers were modified cruiser designs, British Light Carriers were scaled down carrier designs, and Japanese Light Carriers were converted from auxiliary ships. So either way would be backed up by history. But this change would make sense from both an historical standpoint as well as a game standpoint. Historically, there were several nations that were 'cruiser navies' that got into aircraft carriers with only light carriers (granted, these were CVLs purchased from the US or Britain, but it shows that the CVLs fit in with the cruisers and didn't require a capital ship focus for the navy). And within the game, it would be a chance for players to get into the carrier game late in the game when their coastal fleet suddenly has to turn into an oceangoing navy. A perfect example of this is playing as the Italians, but the Soviets are an example as well. Most of the game is spent building a fleet for the Med. The player has no reason to invest in carrier research since patrol bombers and landbased fighters can cover the water zones. Then late in the game you break out into the Atlantic, and you are stalled until you can research multiple carrier techs all the way from the beginning of the tree. This is just something to consider.

If there is anything I can do to assist, please just ask. I could send a revised US air group file to you if you'd like. I love all the work that you've put into this and want to help in any way I can. I know you don't have any currently, but if you are interested, I also have revised division names files for the US (completely overhauled all the division names to be historical) and Germany (revised all the SS division names) and am working on a few others.