Ram, the reason I am under the belief that your ground attack aircraft wont do well is, from the description, it appears to be a bit of a glass cannon, and will likely be extremely slow. Meanwhile, thanks to the size, mass, and retaliative scarcity of our radios(what are they, company level?), it will be of limited utility.
While lack of speed can be a defense against quick opponents, our foe also has weapon systems that can hit it, the bumblebee. So, until we are in a situation where one of the above issues is corrected, I would rather have us design other systems.
Commenting on your other designs, the shotgun appears to me to have issues of its own, notably that it has a cylinder which lessens its power and slows potential reloads. The caliber also makes me itch slightly, but thats not really a major(or even a minor) concern.
The buggy I have issues mostly just with its armament, which appears to be a totally new design in another totally new design.
Now, for my issues with the sub: Mostly the same issues I have with RAM's buggy. Designing a new weapon within a new design. Also, deck weapons are, at this timeframe, mostly obsolete. The lack of snorkel, radio, and similar equipment is also causing me issues.
Finally, nitpicking Funk's mobile AAA: Designing a new weapon in a new design. I also think that we could get a radar system designed in there, although that causes part of my brain to vibrate(and incidentally, brings me to my main issue with this system, that designing more new stuff at once does not have a drawback, atleast none that I can find.)
So, here goes with my suggestion: A variation on Funk's design.
The New Guinean mobile anti-air artillery model of 1952 is a proposed weapon system based upon the AS-T25 chassis and intended to replace the Bumblebee AT/AA system currently in service, armed with twin 3.6in cannon rigged with autoloading systems intended to increase rate of fire by a large percentage. In addition to the standard targeting systems already in use with the bumblebee, the proposal features electronic traverse, a radio to link it with command, and a radio-based rangefinding system linked into the mechanical targeting computer.
The vehicle is also equipped with a simplified system for indirect fire, inorder to allow the system act as makeshift, likely low effectiveness artillery.
Target Cost: 4 Ore, 3 Oil
Type: Vehicle, Medium, Specialized
-edit-
Joe, from what I can tell, more naval guns are listed by shell weight than diameter in inches, followed closely by metric measurements.
Of course, thats after skimming
this list for roughly 120 seconds.