Default Swap on empty partitions?

I have noticed a few partitions which are rather empty and doesn't get used up frequently. For example, the /cache partition and the /dev partition.

Not entirely sure whether the phone would use up those partitions as it seems empty majority of the time. So is it possible to create something which inserts a swap file into those partitions and act as a reserve ram?

Not entirely sure whether a huge amount of reads and writes on those partitions would somehow damage the eMMC chip.