The GCSEs we do today are far too simple, and anyone can agree on this. Most of it is learning based, and I have ZERO problem believing that the ENTIRE country could get A stars if they put in a reasonable amount of effort. It simply isn't that tough, and we shouldn't mistake bad grades for difficulty, but rather for lack of effort.
With this in mind, I'd like to see a tougher paper, rather than a more selective grading system. Differentiating the top marks shouldn't be about careless errors, but application of knowledge, and at the very least, knowledge of the course.
Scoring in the 99th percentile and the 92nd percentile do not distinguish ability, so why should there be a grade differentiating them? Set a really tough paper, where the A star (or 9) mark is at around 70%. Everyone who scores below 40% - give them a blanket grade of unmarkable or something equally bad.
Then watch as suddenly the entire country panics and realizes that in order not to piss away their future, they HAVE to get out of the unmarkable territory.
It will be tough, and students or teachers won't like it. But if it means a country where students actually put in the effort for a solid grade - then I'm all for it.
I envy nations like China and India, where students work their arse off to get the top grade, and in our pathetic country, people screw around all year, waste their time, traumatise their teachers and pass their exams with miserable grades.