Yes, recon planes+transport+a little bit escort for them should remain.
Airforce management: I am happy as well to let Hortlund manage the AF.
Support unit management: Does Hortlund create and distribute them or should players do so with their AP share?
Support units creation: I suggest to focus on sappers only, no artillery. As far as i know, sappers can help at fort construction (right?????), and this is very valuable for the defense of Leningrad. I think whe should limit the TOE of the Artillery units and don't bild too many new ones before the blizzard so they do not steal the ressources from the on map units. What do you suggest?
Organization and leaders: How will this be managed? Will you do everything Hortlund or do all players get their share of the APs?
I'd say that Hortlund could be responsible for creating and distributing support units, plus creating new units and allocating them as needed.
Sappers would be indeed priority for first year, IMHO. And they will be very useful later in war too, when Soviets can concentrate building more artillery.
My suggestion is that Hortlund uses part of APs as STAVKA for support units etc. and after that APs are allocated to players to organize the Fronts and commanders as they wish within APs available. E.g. STAVKA uses 10-20 APs and Front Commanders (players) 10-13 each..depending what is available after STAVKA (after all, we are subordinates to Comrade Stalin.. )
"To meaningless French Idealism, Liberty, Fraternity and Equality...we answer with German Realism, Infantry, Cavalry and Artillery" -Prince von Bülov, 1870-