Guys, I'm not going to argue with you but the technology I mentioned at the top of this thread already exists and is in use in some very busy airspace in this world.
Reading clearances over the air at an airport handling 30-50 departures an hour is not the "all a controller has to do" model of efficiency. PDC (pre-departure clearance) via ACARS/VDL has existed for well over a decade. To only have to contact ATC with a 4 digit validation code is a vast improvement over reading back every word. It absolutely confirms the crew has an exact copy of the flight plan. I won't even get into how efficient it is when a flight plan needs to be modified pre-departure or once airborne.
Second, CPDLC has been in use in the most heavily traveled trans-oceanic airspace in the world for many years, and of course it's primarily satellite-delivered. It cuts down voice traffic by at least 70% for equipped aircraft and allows contant communication versus SELCAL and noisy, difficult to monitor HF radio. More important to this conversation, for oceanic service it's now used globally to relay route changes, altitude change requests, and other instructions to and from the cockpit, and it's in use in high level, en route *domestic* airspace across Canada and in Europe. It isn't the way of the future, it's already here. And believe me, I've seen first-hand both controllers and commercial pilots that don't already fly oceanic routes dip their toes into the CPDLC water with great skepticism only to come away with "that's pretty impressive" comments after a few cycles. And for those that do, being able to stay on CPDLC once into domestic airspace has been widely applauded here.
I get your argument that small aircraft don't need that service and that's true if you're operating in an area covered by conventional voice and radar service, but these types of technology are not initially developed specifically for those operations. Commercial flights using densely packed routes are the bread and butter of the ATC system and providing the safest, most efficient service to airlines is the global goal of ATC providers.
And remember, I did say this system is in use in EN ROUTE high level sectors, leaving terminal and tower services to use conventional voice communications.
I'm not trying to start a war here, I'm simply pointing out that what I said initially is already in use, it's not hear-say or speculation. Get used to it, it's here to stay and will only become more widespread and of course less expensive as it does. As my tagline says, I spent 34 years in this, going from tube-type radios to where we are today first-hand.
Cheers!