When considering the numbers game and possible effect of a large increase in German Fighters there are two points which you might want to think about
a) Operation Bodenplatte
The one time in the late war when the Luftwaffe attacked the allied airforces in Europe in serious numbers. There losses were huge and the damage to the alied forces easily replaced.
b) The ssumption that the RAF and USAAF would have continue on the traditional path despite an increase in the effectiveness on the Luftwaffe
If during 1944 the Luftwaffe had shown an marked improvement I do not believe that the RAF and USAAF would have continued on their historical actions. The RAF alone had a number of aircraft whose production and development could have been increased with little effort, the Hornet, Vampire, Meteor, MB5, Spit 20, Tempest II and Lincoln are the types I have in mind and for the USAAF The P80 and later versions of the P47, P51 and the B29.
For every action there is a reaction, it is wrong to say that one would exist without the other.
One last point it is wrong to believe that the Luftwaffe pilots were trained as well as the RAF and USAAF pilots in 1944. Their quality was decreasing as the other increased due to a lack of fuel, space, people and training aircraft.