I don't think it's really something we can do as messing with vanilla behaviors is kinda... messy and bad.

Maybe @JamieSinn will say it's not messy and bad, but it probably is.

 

Oh god... you don't even want to know.... the amount of lag would massive.

 

Lag as in lag or client-caused player displacement? :3

 

Server lag. Severe, severe, server lag.

 

Sounds fancy. Add it? :p

(Seriously though - why? Is it really that annoying to mess up mechanics that lie extremely deep within the oldest Minecraft code and would also cause client-server irritation? :p)

 

Because it was never intended for this to be done.
Nor is it intended for something like this to be done.

 

See? Would be fun to mess it up. :)

//Sarcasm = off;

 

Fly is a way around this too, you can fly through lava quickly

 

Maybe Pyro++ would be a more suitable addition.

 

+1