Why didn't I ever think to freeze distill water for aquatics and irrigation?
Very smart.
Now for low tech, homestead scale, I think, take a mineral tub, fill with well water in the cold, flip over and empty the tub of ice on a CLEAN surface, scrape any salty ice off the bottom, place in another clean tub, thaw and repeat as needed.
Perhaps once or twice would be enough to remove the majority of issues in well water to begin with.
Then, how to store for later?
Melt and pour into an IBC? Risk of freeze thaws cracking your expensive tote, but it's ready when spring comes
Drain into an underground cistern? install expense of course but if testing proves significant water quality improvement with little embodied labor, perhaps worth it?
My purposes, similarly would be to top off aquatic and aquaponics systems, fish do fine in the well water but evaporation causes plant killing salt build up. Also storage above the swamp cooler to give that some clean water to run on.... hmmm.