Assuming that at Versailles the Germans are allowed a small fighter and reconnaissance air force (handwavery), what effect does this have on rearmament? OTL Germany had some clandestine air units and planning, but had little research into military class engines, which badly affected rearmament in the late 1930's. German industry struggled to produce said engines until late in the war.
Also Germany pretty much had to create an air force general staff and officer corps from scratch, using army officers with little to no experience with the subject to lead the new service. Early on this proved not to be a handicap, but the need to rapidly expand the air service officer corps did limit how many trained leaders could be produced. This also had an effect on how many air units could be trained/formed.
Also the lack of tradition allowed the Luftwaffe to form a new doctrine divorced from the past; here it would have a fighter/intelligence focus for decades before rearmament starts. What would this mean for the Luftwaffe?