To re-implement the University application process would indeed be a huge amount of work.
However, the governing principal of Cambridge University, for example, is that all operations are done at a human scale, and I think when you factor in the large numbers of staff whose labour the Universities have access to, it becomes possible.
For a group of applicants for Computer Science at a Cambridge college, for example, you would have a Director of Studies and one or two other staff ranking around 20 applicants for half as many places. (The ratio of applicants to places is much higher prior to interview.) It is a tractable problem to solve, even if for other institutions the process is scaled by 2x/3x (4:1 / 6:1, up to Nottingham’s reputed 13:1) or maybe even more.
An idea we mooted over dinner last night was for these applicant rankings to be fed to UCAS — the University and Colleges Admissions Service — and for UCAS to combine these rankings with the applicant preferences to fill up each course from the top down. No need for grades, just use the desirability metric provided by the institutions.
Grades themselves are a strange beast. By their nature they are different to raw marks. A grade speaks to your ability as part of the entire cohort of examined pupils in that subject. Without the exam, taken nationally under examination conditions, it just doesn’t seem to make sense to refer to grades.
If we called them “exam grades” perhaps the folly of trying to assign them to pupils, who have not actually taken an exam, would be clearer.
(I speak with no real authority, but I am a high school teacher in England.)