I agree there should have been a maximum moderation of +- one grade.
CAGs do seem the fairest way - I disagree about mocks though, which are absolutely useless to anyone who hadn't taken them yet, or whose school don't have the space available to do them in exam conditions, or who didn't work hard for them because they had university interviews or tests around the same time etc etc.
Two other things that are hugely problematic I think - firstly no individual appeals and no information about appeals, which leaves so many children not knowing what's happening next. And secondly the decision to use CAGs for small cohorts - while I understand why that might have briefly seemed like a good idea - it was obviously going to advantage private schools. The larger increase in A/A star grades at private schools compared to everyone else is an absolute disgrace, as is the fact that as far as I know, no minister is admitting that it's a problem.
Anecdata alert, but a poster yesterday mentioned an independent school near them, rated inadequate but with a very small sixth form, where they got 24% A / A star, up from 0% last year. And meanwhile friends are telling me of students in poor performing schools in disadvantaged areas, holding oxbridge offers having interviewed and taken tests, missing out by two or more grades because of their school's past performance. Those university places have been taken from disadvantaged but deserving students, who having chosen their secondary school, were unknowingly then in a position where they could never get to oxbridge. Whatever they did, however hard they worked, the A* they needed simply wasn't possible with the current algorithm. Maddening.
(I think the 'best' example I've heard of downgrading was a student doing Spanish, she is 19 having spent a year in Madrid after GCSEs, fluent in Spanish, predicted B, moderated to a U based on prior GCSE attainment)