Here's an idea. introduce gmo or starving children upgrades to improve the food to unit ratio.
Like upgrading the gmo will make 1 food worth 2 units, and stack multiplicativly 1:2 then 1:4 then 1:8.
And upgrading the starving children upgrade will increase the amount of units you get from 1 food by 1, but will sacrifice a little bit of that unit types total income.
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