This will be good, but I have a quick question.
Does Sidious have any military commanders at his disposal? Tarkin? Veers? Piett?
I'd take Thrawn over any of your mentioned commanders.
In a one-on-one, I'd probably go with the Emperor to be honest. He's supposed to have taken the power of an entire planet into himself. Palpatine, as insanely powerful as he was, never did that.