Gable Vent Fan to Make Usable Attic Storage Space - Useful or Trouble?
You'll increase energy costs and only make it marginally cooler. The only way this could work is to fully insulate and make it part of the conditioned space. But the kitchen ceiling/attic floor is not designed to support any kind of real loads, so it's only practical to store very lightweight items anyway.

So what lightweight items can you store there? If conditioned space, anything that will fit through the access. If not conditioned, only items that can withstand extreme heat without degradation could be stored there. I would not store any valuable clothing in that kind of environment.