Thing is, I don't remember there being anything particularly wrong with the previous standard grades and highers system. 8 standard grades was about right to allow you to still have a fairly broad range but also be able to specialise - I suspect this depended a bit on timetabling and varied between schools but from memory my school went something like:
Compulsory standard grades - English, Maths and whatever language you did in 1st and 2nd year
then 5 columns to choose from:
1: History, geography, possibly business management IIRC
2:Biology, chemistry, physics, I think there might have been a general science too.
3: Arty/active subjects - Drama, music, art, graphic design, home economics, PE..
4: Bit mixed - accounts, business, at least 1 of the sciences, computing
5: very broad - included history, French or German as a second language, I think 2 of the 3 sciences, music, art
I've doubtless forgotten some! But essentially on top of English, Maths and a Language you had to take a science, a humanities type subject and something a bit more arty/creative. You could do 3 sciences, or 2 languages, and still have a good mix. There weren't that many impossible combinations.
On top of that you had compulsory but non-examined PE, RME and PSHE.
(p.s. I know lots of people will remember this themselves, more for the benefit of those who've not experienced the previous system)