Distilled or softened water 50/50 with antifreeze is fine. You just have to check for electrolysis. Not sure if this is needed?
To address the point you added about potentially not needing the anode - no matter what we do, some amount of electrolysis is going to occur in the cooling systems.
So, knowing that some level of corrosion is going to occur what part do YOU want being eaten away? The aluminum of the radiator or the zinc sacrificial anode? Not only is it a heck of a lot easier to replace the anode drain plug once its been eaten away to a certain point, the radiator will never burst because the anode has been eaten away to a certain point. Once electrolysis has eaten the radiator away to a point, it WILL burst every time.
There is a reason every boat, bridge, lock, dam, other piece of metal submerged in water have sacrificial zinc anodes attached to them - because when properly installed and maintained they just plain work.