7) Katyusha-like artillery
+ negates their artillery advantage somewhat
What we would want is Nebelwerfer, not Katyusha. Katyusha is big, it has to be mounted on truck, Nebelwerfers could be dissasembled and used in mountains (so they would serve also as mobile artillery), also mounted on trucks like Katyushas.
Instead of a floatplane biplane or an autogyro I propose light liason/bomber high-wing monoplane.
AS-FI29 is a small, high wing monoplane 2-seater liason aircraft, capable of carrying another 4 people in cargo compartment or up to 200kg bombs. Only it's frame is built out of metal, the rest is made of cloth and wood. It uses 9 cylinder engine, similar to the one used in AS-DB-HF-23, but upgraded with lastest technology. It's only weapon is AS-1924 machine gun mounted behind crew cabin.The plane is capable of extremly short takeoff and landing, 60m and 20m respectively. The plane can be used as officer (spy) transport, air ambulance, light cargo(including mail and ammunition) delivery and battlefield reconnaissance. Equipped with radio by default.
Basically nice all-around Fi-156 (I'm not shitting you about the takeoff and landing distances, Fi-156 could manage to land
backwards when wind was right), theoretically more useful than a hydroplane because it can be used basically everywhere. I refuse to accept that we can't make 60m clearings in the jungle, or that there are none for that matter. Also, the Charles Carpenter guy someone mentioned before, the one who was raining bazooka fire on Germans during WWII was using what was basically an American version of Fi-156.
EDIT: Also, as for armed autogyros...
They tried that, but it was quickly deemed that autogyros are way too unstable to be useful in any form of combat, sans innacurate bombing maybe, and even then they would be very, VERY,
VERY easy prey to enemy AA guns, even the pintle mounted ones.