Why not a 20% tax rate with 10% unrest?
You know that the 0% tax already comes with 10% unrest, right?
Personally, I think that the taxes are not granular enough as well, but if you play the game, you will notice that the buildings are nicely balanced against the unrest for different tax levels. I would welcome a change that gives me some taxes at a lower unrest penalty, but I doubt it will happen.
I already seldom move the tax slider from 'None' until turn 60 or so. In my current play-through, it's still at 'None' on turn 96.