If possible the ablity to activate Zram or Zswap from the panel and monitor under server information.

I know these are easy to implement, without Plesk but would be a neat feature. These are both implemented in most Kernels now anyway and not activating at least one seems to be leaving server performance on the table.

Ability to configure Swap size and compression algo and monitor.

Default swap size 50% of Ram seems to work great as a default.