SOE aside (although I'm eagerly looking forward to it's release!) my own favored lighter-than-air tech tree begins with balloons: land units, MF=1 (I even use a Wagon "Run" anim for its movement) which have the "radar" ability (think early military uses to see over the horizon).
I use rigid frame airships as longer-range-than-biplane light bombers & scouts with very low DF and the "detect invisible for subs" Wyrm suggests. An interesting note: the only helium reserve (basically in a huge underground cavern) is in the USA, which refused to export any to Germany (or anyone else for that matter). Hence hydrogen and the inevitable Hindenburg-style accident. So "American" Zeppelins (really whoever controls the helium resource) should have a higher DF.
I also basically use barrage balloons as Civinator describes: an immobile "fighter" for bomber defense.
Note that there is no meaningful upgrade path among these.
And, yes, I agree with Ivan the Kulak: having an ""attack enemy aerial recon assets" air mission would be sweet.
- And, fnally, whenever SOP comes along, I'm keeping my fingers crossed for a "War Plan Orange" scenario with the Akron & Macon!
With Thanks Again To Wyrmshadow,
Oz