I also like the spirit of shared inquiry on this list. As you
probably know there are other Buddhist-related Yahoo! groups, but
there, I find, the postings often degenerate into manifestos of fixed
positions. The Pali list is, if you like, a list for people like me,
who DON'T know everything yet!
Oskar von Hinueber's "Handbook of Pali Literature" doesn't mention
ANY translations of the Niddesa into ANY modern languages, so I think
it highly unlikely that you'll find it on the internet in a language
other than Pali.
I seem to remember reading somewhere that Mrs Carolyn Rhys Davids had
put forward a theory that there once was a 10-fold path, but even
after looking through my books I can't find a reference for you.
The debate about whether the jhaana-s are necessary seems to have
begun possibly even during the Buddha's own lifetime. Certainly it's
still hotly contested today. I doubt that anything I could say would
bring this 2,500-year-old debate to an end! But if you're looking for
practical instruction, there is an Australian monk named Ajahn
Brahmavamso (sp?) who gives courses on "how to jhaana."
So, no satisfactory answers from me, I'm afraid ... but re the
A.t.thaka Vagga and its precise relation to the dhamma as we know it
from the nikaaya-s, I just have one observation to make, and that is
this: I think it would take an entire PhD dissertation to really go
into this question and all its ramifications, and the end result
would be a set of possibilities and probabilities rather than any
convicing and definite conclusions.