Theoretical Baking

Entertain this thought with me: what if I were able to bake more (and more easily) by supplementing my ingredient stash with dining hall offerings? 

For example, I just found a recipe for a banana cake that uses these ingredients:
2 2/3 c. all-purpose flour minus 2.5 tablespoons
2 2/3 c. sugar
3/4 tsp. baking powder
1 1/2 tsp. baking soda
1 tsp. kosher salt
3 large or 4 small very ripe bananas
3 eggs
1/2 c. buttermilk
3/4 c. canola oil
1 1/2 tsp. vanilla extract

Of those, I lack buttermilk and bananas.

The rules of the dining hall permit taking one piece of fruit per diner per meal with you when leaving the dining hall, and it’s quite a common practice to bring your own cup and fill it up before you leave.  So what if, theoretically, I got two (well, two large or three small) friends to each take a banana with them when they left, and I brought a lidded cup, filled it with milk, squeezed a sufficient number of lemon slices from the hot tea area into the milk to make homemade buttermilk, and nabbed a banana myself?

Theoretically, then, this banana cake wouldn’t even require a trip to the store, which would, in a very non-theoretical way, be delicious.