next thing we know you'll be allowed to clear us for the ILS without first wasting RT time by clearing us for the loc, us reporting established on the loc, you clearing us down the slope, us acknowledging that clearance etc etc.....
I'd love to say "Cleared ILS" tomorrow if it meant "don't descend to 2500ft below the glide path and hit the low level traffic working Thames" and it was understood by all nationalities of pilots. RT saving would be immense on a busy frequency. "When established localiser descend on the ILS", introduced a while ago, is a bit of a mouthful and gets varying responses!
One of the problems with "cleared ILS" is that you could still be at 4000ft on the closing heading with City traffic at 3000ft. When do you descend to if I say "Cleared ILS?
Finally, in answer to your point about all the acknowledgements, missed readbacks are a major cause of incidents in ATC, and we're to blame (mostly) if we get it wrong - that's why we need the (correct) acknowledgement
Edited for spooling mistakes