See that is where you’re wrong… completely. A part of a whole is still a part, but the whole itself is a different entity itself. When describing TF2(pub play), one has to realize that all parts of the team make up its own identity. If you look at a cell, you don’t call it a mitochondria, because a mitochondria is a part of the cell. Rock Paper Scissors all represent a difference and not linked in anyway.
Plant cells are pretty much reverse engineered to animal cells. Without plant cells, all animal cells would die, without animal cells all plant cells will die. They work in unity, and thus apart of a system, and not single entities independent from each other. So, you cannot use the rock paper scissor argument when looking at classes.
The greatest reason for classes, is to promote teamwork, to make an individual directly or indirectly work together. If that is not the goal, then problems with balance will arise.