Dusty old SIMPSON quotes aside, I can say that, as a nerd, I speak with experience on what is nerdy.

And I can't say I agree with any of that... to me, the whole point is hearing people doing voice work that, apart from Yoda and the Emperor, are doing a very good job emulating the actors they are dubbing, which to me is what makes it funny. If you're going to go the route of having Yoda not sound like Yoda, why bother with sounding like the other actors?

Having Yoda sound like a young girl is something a random dude with a camcorder making a $100 horror movie would do.. it just comes across as too easy to do. Or I guess to put it another way, it's something Jimmy Fallon would do.

I would either go the goofy route with all of them, or have all of them sound like their original selves as much as possible.

But, to quote someone far more famous than me: that's just me, I could be wrong.