Um... Eagle... Those things you speak of us "already having" didn't exist right from the very beginning of this game... They were all added. You've been around for at least almost four years. How'd you miss that?
When ANY plane series gets its facelift, it stands to reason that new models of it, when applicable, should be added. The staff has all the paperwork and such for the series laying out there in the open, and they're probably more familiar with them at that time than any other. Why not add other models then and there?
Just saying, you're gonna need a different argument.
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Anyway,
My favorite plane is already taken care of, so I really don't have a strong personal preference for what is next. However, if CT is ever in a million years going to be released, I'd think they'd concentrate on upgrading the remainder of the ETO lineup before working on something else.
The Typhoon, Tempest, Ta152, and I believe a few bombers, still need to be upgraded for CT to look nice all around. I suppose since it's 8th AF, the Typhoon and Tempest could wait, but I also suppose that there will be AI squads flying those, and thus they could use the facelift.
Really though I would love to have more Japanese aircraft to enable different scenarios and AvA setups. It's kind of hard to do things like Rabaul when half the aircraft fighting over it are nowhere to be found in this game (check my sig for why I might want to do such a scenario

)
More Russian aircraft would also be great, as would more Italian planes.
But, I remember Air Warrior III, and how we never got a new map or plane for it. Aces High works great for me in that respect. I can't even count how many planes have been added in the short time I've been around.