With the current nuclear war causing 0 food production in the game, a glaringly obvious problem has been exposed. That is, there is no way to bring food into the game and thus I propose a new improvement.
The Underground Farm
The UF would cost 25 lead (to protect against radiation) and $250,000.00 to build. It would require electricity (for the grow lights). The upkeep on the UF would be $400 per turn. The UF would provide 4 food per turn with a limit of 5 UFs and standard production bonuses bringing maximal food production to 30 food per turn at a cost of $2,000 per turn.
Such an improvement could potentially improve player retention as new players are able to produce food even without alliance/market support.