WWII German observation planes.

Well that depends on your unit definition level. At the company level, no. But they almost certainly would be attached to a higher level element such as divisional. Rommel had a habit of taking his Storch forward of his units then landing at the closest unit to direct them. 

But mind you, such a scenario as you envision would be spread out. The aircraft, officer group, and vehicles would not be in one tight group. They would be dispersed for tactical reasons. 

Rommel used a storch to get around and where Rommel was, I'm sure there was armor.

https://goo.gl/images/e35Luu

Observation aircraft like the Storch were operate at Corps level. They would have landed to comunicate with ground commanders, but as Stik says, vehicle would be spread out. You could get away with having 1 command vehicle within the scene.

I think there are some possibilities in 1/72.

There's the Storck, more of a liason aircraft.

Then there's the true recon aircraft.

FW 189 is easy to get in that scale. it's a maximum cool aircraft

Also BV 141, Hs 126.

As for the tracky things, 250's, 231's in both 6 and 8 rad. Tanks till you give in.

Good dio scale too.

Yes, but you lose much of the effect with 1:72 figures. 1:35 is the best scale for figures and vehicles, but again you’re reduced to the Storch and then there is the base size consideration. 1:48 is the best compromise, and Tamiya does make some suitable vehicles. Those other aircraft you mention would be less likely to land at a forward mobile CP site due to their lack of STOL capability, and would likely communicate more by radio. 

Hasegawa made a 1/32 storch with a rommel figure.  Might be close enough with a 1/35 kublewagon or other staff car.

Tristar released a 1/35 FI-156.  It is now available under the Hobby Boss label.

In 35th this would be a large dio, especially when leaving space between vehicle and aircraft. My largest 35th armour diorama's are my Jagdpanther and E-100 Jag and they would not be big enough.

personally, i would go with 72nd for this, i plan on doing one similar myself with a Storch. For a Polish setting, there is a company called first to fight which has a selection of German vehicles from the Polish campaign. They include a 251/6 and Pz I command tank, both of which would be ideal.

Realistically speaking, at most, if you’re going to have the aircraft as an element of any diorama, you’re just going to have a vehicle come out to the aircraft to move any pilot and passengers between the landing spot and the CP. You don’t want the aircraft at the CP due to noise and prop wash, not mention the chance of damage to the aircraft thru collision with wires, antennas, etc.

A diorama of the Gran Sasso operation would be nice. Skorzeny originally planned to use a Fa 223 helicopter, but substituted a Storck after the first aircraft broke down.