root partition wont allow to go lower, So I think its the smallest we can get.
But will try to cleanup the OS again, see if I can reduse more.
Why do not you use a lighter linux system like Lubuntu or even, a linux system even more minimalist as there are at least a dozen ...
I know, I say in a vacuum and it's a lot of work but I have often thought about it. I did not have the courage or the motivation to try.
These days, I'm getting ready to make my RIG fatter because 2 GPU is good for testing, but it does not produce enough and not fast enough for my taste.