That's quite the massive idea.
The one challenging idea that may be a problem is all the races, save the Dremora of course. There is a lot of crap about facegen, and I think the body is always default. Not so 'unseamless' as the last game's bodies.
That's the only thing I find quite challenging so far... And it may be completely simple when I get to use the CS. The rest could be done quite feasabley. But you need good voice actors for a good mod, especially for Oblivion.
I can be a texturer and general CS person.