Thats kinda the point of this whole thing is to make them more usefull
It would not make them useful. It would break the game.
In order to make such a system work HTC would need to add aircraft that saw limited or no service and forcibly balance sides, which means, by Lusche's numbers, 2 out of 10 players would be forced into Axis aircraft when they wanted Allied aircraft.
Required additions:
Aircraft:
A7M2 'Sam': Japanese carrier fighter intended to replace the A6M, 7 prototypes built, no service
B7A 'Grace': Potent Japanese carrier bomber and torpedo plane, 114 built, all carriers lost before entering service
G8N1 'Rita': Japanese heavy bomber that never got past prototype stage due to the end of the war
H8K2 ''Emily': Japanese flying boat that could be used as a heavy bomber with good defenses, 112 built, heavy use
He177A-5: German quasi-heavy bomber, about 1100 built, light use due to persistent reliability issues
Meteor Mk III: British jet fighter, few built, no air-to-air combat versus manned aircraft
P.108: Italian heavy bomber, 24 built, light use
Note: Allies possession of the B-29A would hopefully be balanced by the Axis possession of the Me163B
GVs:
M26 Pershing: American heavy tank, only 20 saw combat in WWII per wiki
Skink: Canadian quad 20mm AA vehicle build on a Sherman chassis, per wiki 1 saw combat
Boats:
S-Boot: German fast torpedo boat
Allow Axis fleets to have proximity fuses or remove proximity fuses from the Allies. For fleet survivability the prior is better for gameplay, for historical accuracy the latter is better.