Tim O'Connor wrote:

It would be lovely to have a standard draft gear box and coupler shank
design to fit it, such that every coupler would sit properly in the
box and not droop! But even as practical as that would be for
virtually ALL modelers, what are the chances of getting such a
standard accepted?

If you don't write that standard, the chances are zero.
Tony Thompson

I hope that you meant the collective "you" and not me personally.
I certainly do not believe that I am the first person to think of
it, nor does the hobby lack the talent to produce such standards.
And as Pieter pointed out, there's an existing RP -- it just needs
to be brought up to date!

Tim