ORIGINAL: BrianG
Luftwaffe 2 choices:
The only choice is a promotion of crap flyer to this hq.
Richtofen is almost as good - but you would rather keep him in FKVIII.
One suggestion given to me by EwaldvonKleist was to just use Loehr who is almost as good. You can transfer up to 16 airbases including all of FKVIII into Luftflotte 4. So really you only need one good Luftflotte commander. And the costs of doing those transfers is less then appointing a different commander? You do not need HQs to be close like you do for ground commands. And anything in Luftflotte 4 will support all army groups and nations - not just AGS or Germans.
Personally I would advise for OKH and army groups the ones with the highest morale who are not good enough for corps command or are GFMs and cannot be in corps command. The latter means Reichenau, vKluge, and Kesselring.