Regarding the ‘upkeep’ mechanic I immediately thought of Le Havre. Not sure if you guys are familiar with it, but this game uses this mechanic in a slightly modified way to what you were explaining. The ‘upkeep’ is paid at the end of a series of turns (at the end of the round), so while you are concerned with having enough food for your workers you don’t have to pay it each turn. Also you may use either food (of which there are a few types) or money to make sure your workers get fed. It’s interesting because as you’d mentioned the resources are now duel purpose, but it becomes another level to your strategy to decide which resource you can afford to use at the end of the round for this purpose. Another aspect is as you build ships which is a core part of the game; you spend less to feed your workers since the ships provide a base amount of food for your workers.