I think that what it comes down to is that, as designed, the Aquila should not be the equal of the Yorktown (80+), Ark Royal (72 as designed, 60 in practice), or Soryu (63+) which are the in-game analogs they would be compared against. Even with the folding-wing version of the Re.2001 the Aquila was projected at 51 plus 15 hanging from the overhead. But if the Aquila given by the Focus is at 3*20=60 it would be equivalent to them.
Aircraft carrier capacity is a tricky one to sort out - and historical numbers can be misleading. For example, in my notes I have three air wing figures for
Yorktown during WW2, 31 Dec 1941 (69), Coral Sea (71) and Midway (76, plus three spares stowed overhead) - although I sadly don't have the hangar space (and it's a bit late for me to hit the bookshelf).
Ark Royal, on the other hand, often carried significantly fewer than 60, due to the FAA getting short shrift when it came to aircraft acquisition, despite having a hangar floor area about twice the size of the Lexington (70 and 75 air wing size in the two entries in my notes) which had a hangar floor area, at least according to my notes (the figure is from Jordan's
Warships after Washington) similar in size to the
Aquila - although the Lexington had 50m more of flight deck to play with when it came to the deck park. Another important thing when looking at
Ark Royal's air group is that it was prior to the use of a deck park, and so not really comparable (in terms of "total effective capacity" to figures used with a deck park (which is every US carrier).
It gets even more complicated when adding in the capacity to store munitions - despite having a smaller designed air complement (and a substantially larger hangar, although 44m shorter flight deck)
Ark Royal only carried about 12% less fuel than
Lexington (sadly, I don't have a figure for Aquila), and the ability to carry fuel and munitions (again, I don't have a figure for Aquila) for the aircraft (to enable repeat sorties) is also important - although doctrine and capacity for resupply also comes into play here as well.
Given that
Aquila is actually a bigger ship than the Yorktowns (although certainly less optimised for aircraft operations), and everything else that's been discussed, I still think it's plausible (noting that this is a very "wet finger in the air" guess - I haven't gone through the plans or anything like that) that, with some practice operating aircraft from a ship, she could have operated 60. By way of how these things could improve, the UK Illustrious class started operating air groups in the mid-30s, but by 1944 at times operated air wings of 57 (flying Corsairs and Barracudas) - and that's with half the fuel capacity of
Ark Royal. Part of this was shifting to using a deck park, but I expect experience and optimisation played a part. In this context, I'm a bit reluctant to suggest a max air wing of 40 for a 27,800 ton ship (normal displacement) with the (admittedly small) hangar size of
Lexington - but, as I've said before, there's a case to be made in both directions. I just thought I'd throw some more numbers in the mix for discussion