Add this command just like PC edition as it doesn't need mods or server software to work as it is implemented as a official PC command
This is not the mcpe forums. You should contact the developers of mcpe or Mojang AB about that, since as you said, it shouldn't require server software to be implemented.
The client is not able to implement this. Gamerules change server behavior. Actually, a server fork, more especially @thebigsmileXD is working on implementing this in CS. No advertisment.