The fact that I can write out my clearance before I speak to ATC (less code) suggests to me that there is not a great deal of thought that needs to go into its construction. Guess what - today I'm cleared to blah, I'm heading up the coast so it's 34R with a SYD 1 Departure, maintain 3000' and Departures frq 123.0 Minor variations on a theme only.
On some routes (CBR-SYD) for example, there are standard clearances, including SID and STAR. If ATC can manage that scenario, what is the risk posed by an unlicensed controller issuing the clearance???
It still falls to the ground, tower and en route controllers (licensed) to ensure separation and direct aircraft in CTA/CTR - the worst thing that can happen here is that an aircraft is issued an incorrect or incomplete clearance, in which case a competent flight crew should pick it up (they have to fly what they're given!)
If I'm a little too innocent in these black arts: all apologies - I'm happy to listen to reasons why this poses a massive risk, but most days it wouldn't make a difference to me if I was listening to a recorded message.