I've spent some hours this weekend thinking about the Brandenburgers on the Eastern Front. A sample 'Generic' Brandenburger battalion is attached below.
The overall concept is to allow rapid infiltration ahead of the rest of the German Army. This is what the Brandenburgers were designed to do (especially to seize airfields, bridges, road junctions, etc.). Historically, they accomplished this usually by speedy overland movement. They did not conduct large airborne operations very often (if at all). Small airdrops on a scale probably not noticeable at the Directive 21 scale were conducted more often, although still pretty rare. Mainly, the Brandenburgers on the Eastern Front operated as fast special-operations ground troops (for example, it was Brandenburgers that raced ahead of von Manstein's 56th Panzer Corps to seize the crucial bridge across the Dvina River in late June, 1941).
Notes pertaining to the attached screenshot:
Proficiency = 90% (befitting some of the most highly-skilled elite troops in the German Army)
27x Recon Rifle Teams (not sure if these teams represent 4 or 10 men, but since they are called 'Teams' by TOAW then I'm guessing 4 men per team)
27x Jeeps (actually, these would be Kuebelwagons, but they are functionally equivalent to jeeps)
9x Assault Squads (these represent the heavy hitters in case stealth and surprise aren't enough to seize the objective. I originally thought about making all the squads/teams into Assault squads/teams, but now I think that that would be misrepresting them by showing them as a heavy combat force when actually they achieved most of their objectives using speed and surprise).
4x HMGs + 6x 50mm Mortars + 2x 81mm Mortars (represent the heavy weapons company)
21x Trucks (fully motorizes the battalion, giving the battalion the maximum speed of 33, which is absolutely historically justifiable)
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Addendum: I would severely limit all Axis airborne operations on the Eastern Front (not just Brandenburgers). After the heavy casualties suffered by 7th Fliegerdivision on Crete, Hitler opposed pretty much all airborne operations. After Crete, German airborne operations basically ceased. This should be reflected in Directive 21.]
Total strength of the battalion is about 400-600 men (depending on how TOAW determines the size of the recon teams).
EDIT: One final note: I would set the 'Replacement Priority' for the Brandenburgers to 'Very Low', which should make replacing these elite troops more difficult if they suffer losses.