TheoOdo said:

I always assumed that Palpatine was simply thousands of years old, explaining his severely withered face.

i always thought that it would add to yoda's legend that yoda slew the last sith, (which would be really old palpatine) but failed, which could introduce an entire revenge subplot. (perhaps even an opening prologue to the saga?)

PERSONALLY, i never like the idea of the SITH, as they are never mentioned by name in the OT (i know they are in the script and the novels). I really just like the idea that Jedi as a whole sometimes just go bad.

SIDIOUS was perhaps just a mastermind bad jedi. Maybe once on the council, maybe even Yoda's old master? Thinking like captain black from captain scarlet.