Unless they manage to keep us from getting the Jungle's resources next turn, we should hit three oil and thusly be able to mass produce the Model 2 Hornet, meaning we'll have even numbers advantage in the air
and a better fighter. Even if we loose the Mountain's Ore income for the turn, we'll be getting a replacement ore from the jungle, and so we'll remain even on that.
The combination of more fighters and not actually decreasing in ore even if we loose the mountain's income means that while an AA gun could be very useful, I don't think we actually need one.
For dealing with the whole air raid thing, since they lack a proper bomber, I think what we should do is spend our Reversion Phase to get Armored Trains just like the other side has, that should deal with it.
Alright, for the expense credit, let's start making the Hornet cheaper. That'll push the damn Arstotzkans back. Also, would that design allow our pintle-mounted MGs on the Smasher to function as light AA weapons as well?
With the Oil Income from the Jungle it should already be cheaper next turn, spending the expense credit on it would be a waste. On the other hand, if we spend it on the Smasher, as that would make the Smasher easy to produce. We should have 2 Ore, 3 Oil next turn if we loose the mountain's income. If we keep it, we'll have 3 Ore and 3 Oil. A Smasher costs Costs 4 ore, 2 oil. Spend that expense credit on making it cheaper and, well, who likes the sound of mass produced tanks?