first, spend millions to install repeaters on ATC communications systems, so that everyone talking to that controller, regardless of frequency, can hear everyone else.
That should not cost millions. All that is needed is for the receive audio from each receiver in a group to be fed to every transmitter in a group, along with a PTT signal derived from the presence of audio from any receiver. We used to rig a similar facility in television outside broadcasting, especially on Golfs, so that everyone listening to the director could also hear everyone else calling in.
a two-step process for controllers to use with every transmission: first, don't move your lips before you push the button...second, after you push the button, move your lips....
Good advice for all of us, and to be fair, I find it is usually us pilots who are much worse than the controllers. An RT set will not transmit instantly; it will take a fraction of a second to check its frequency is correct and stable before transmitting, so if you start to talk at the same instant that you press the PTT, your first word will be clipped, leading to "station calling?" and having to repeat it all again or simply being ignored.
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