The only games times I can think of where games use slot cost is when the inventory is a grid, and certain items are bigger and take up more space in the inventory. However, size of the item is almost never taken into consideration when equipping that item. - think Diablo 2 inventory, or Resident Evil.

instead, tanaka implements a number crunching system where we have to use algebra to figure out what is the most efficient combination of accessories. We can no longer just look at stats of two items and take the one that has better stats. now we have to solve for X....