I don't see any reference to Gregory at Cambridge Tony
http://en.wikipedia.org/wiki/James_Gregory_%28mathematician%29
I think the biggest handicap is the language, the nomenclature and the symbolism.
What techniques of Newton's mathematics do you see as outside of today's A level curriculum?
Complex numbers, calculus, infinite series, logarithms all of these are solidly in the A-level syllabus today
You might well say that A level maths is firmly rooted in the 17th and 18th century.