It probably shouldn't be a gamerule but for now it can be so we don't have to deal with saving and loading to and from disk

if were having an overlay on where you're going to place the block couldn't we just use the mouse wheel to change the distance? And have a default value of 3 or 5 blocks?

Why would we load from disk?
Edit: I dont think saving the /airplace reach is needed if you are talking about that

Having to set the reach every time you boot the game will get really annoying

if were having an overlay on where you're going to place the block couldn't we just use the mouse wheel to change the distance? And have a default value of 3 or 5 blocks?

no, the mouse wheel is already in use and being able to just set the players reach is easier

Will see what I can do!

UPDATE: Configurable AirPlace Reach is gonna have to be tied to the command rather than a new gamerule.

AirPlace is handled using the doItemUse method. This method is called client-side, while gamerules are handled server-side. This is a problem because the client does not have access to the gamerules (unless the player is playing in Single Player).

Usage of gamerules is a bad idea in case we decide to fully support multiplayer in the future.

I am not shure if it is bad but you could just put simple informations like reach in the NBT data of the player.

Merged. Please close this issue @Matthias1590