I had to resort to the seaguls; Fast forward - spamming research, the first auto-cannon option (not the ammo) comes after approximately 4 months of research. No idea which string of researches unlocked it (it unlocked the 30mm cannon + parts + ammo).
With seaguls, I have to avoid all "very small" craft but on the upside, the speedster can down all small and most medium crafts without taking damage.
For the tanks, that's seems to be really far. I fast-tracked all of my current research topics (~8 months) and I haven't unlocked anything tank related. There are items missing apparently, although it's not any help, the lab is 20000% overworked already.
However, I used the drill on the Gray codex. A month ot so later, I get a satelite mission (- lots of infamy if I ignore) that I have no idea how to do. Tried commissioning Skyranger, Jellyfish, Snake and Shadowbat but the game tells me those crafts can not be used for that mission. On clicking to the "What to wear?" hint, I get a "We can use the following : Unknown" tip. Curious as to what tech is needed to be able to go to the South pole and do the freaking thing.