Fair doos, no offence taken at all

HSTEd's mystical ECP wouldn't really help with freight, you don't want the brakes applying 'instantly', (at worst) you'd end up in a heap, or (at best) constantly be delaying following traffic while making several standing starts in a row!
You misunderstand, you set 10% brake force and you get 10% of the rated brake force immediately.
You set 1% brake force and you get 1% brake force
You can alter the brake force at any time and not have to wait for a several hundred metre pipe to alter its pressure.
You can even make vehicle number 100 in the train brake a completely different amount if you want for whatever reason, and you can receive feedback as to the condition of the brakes in any vehicle on the fly.
The current air braking system works perfectly well, it's set up so as to give the smoothest possible application in the available signal spacings we encounter.
So having the braking in the last wagon applying several seconds after the brakes in the locomotive is a good idea? Or the brakes in the last wagon releasing several seconds after the brakes in the locomotive? Or the brake force not automatically altering based on actual vehicle weight at the time of the braking or to account for any problems with the brakes that might alter its effective braking effort.
This sort of thing snatches couplings and risks derailments from wagons ramming each other hard during severe braking.
Actual Federal Railroad Administration figures for operating railroads in North America and South Africa that are using ECP technology show reductions in coupling breaks, massive reduction in stopping distances, reduction in brake wear, reduction in the incidence of wheel-flats and reductions in fuel consumption.
Oh and the same connectors that carry all these brake signals and power for the electronic equipment can carry signals for hard-line based Locotrol type systems. In other words, you get multiple working capability
through any freight train.
This system is in use in several places around the world today, it is far from 'mythical'
Twelve thousand feet...? I think you've made a typo there HSTEd!
Welcome to North America.
I can assure you from doing the job myself that a light engine stops in a lot shorter distance than the two to three thousand ton freight trains I drive day in, day out.
Yes, because you have inefficient braking systems that cannot develop the maximum available brake force to avoid sliding throughout the train.
The laws of physics dictate the stopping distances for a certain set of conditions, to a large extent they do not care how your train weight is distributed.
Maximum possible brake force is determined by axle weight, which is determined by vehicle weight.
It doesn't care if your weight is made up of locomotive or stone.
(20,000t 6,000ft long BNSF Taconite trains fitted with ECP brakes have been demonstrated stopping in 550m from ~40mph - which while not as fast as a light locomotive is still very very impressive considering that was not an emergency brake application - for reference this complies with the relevant Railway Group Standards.)
(Most of our current stone trains are just over a thousand feet in length by the way).
Which is why railfreight in the UK is dying (or would without rather large subsidies).
The trains are all too short.