Flying in Survival Minecraft (3rd party game modification)

I'm sure that Mojang knows about hacked clients and being able to fly on servers, as it's been possible for a long period of time. However, I wanted to report it anyways as no one else has, as far as I see. I do feel that it needs patching, as it's an unfair advantage to others.

I also understand that this is not the base, unmodded version of Minecraft, but it does however change the way it is played from a base, unmodded Minecraft server like Vanilla servers to someone who is using this client.

Information:
-The client / server will eventually kick you for flying if flying is not enabled
-Using any flying modification will not change the player's flying tag in the abilities section of the player.dat formatting
-Riding elytra does not set your flying score to 1, so it shouldn't interfere with fixing this problem

Some suggestions that could be used to fix this problem:
-Track player's flying attributes who have any game mode because it seems that it's currently only being tracked while in creative mode, then automatically kick players from the client that are both in survival mode and have a flying attribute score of 1
-Make flying server-side instead of client-side so that any modification to the client will not have an affect on being able to use flying hacks

Here's a video I made, showing how the attribute scores do not change with a hacked client in 1.8, as well as elytra in the 1.9 snapshots https://www.youtube.com/watch?v=xH_Z6wqWAK0