It must be a great place to escape to.
Mid winter pipe damage to the main residence is a concern
I am not sure if you are talking about two different structures. It would seem like with a hand pump in the kitchen that the amount of plumbing that you have is very minimal and the water is not under pressure even if the pipes do crack. But with a system that old you might want to make sure that the pipes are not made out of lead that could be contaminating your water.
Two structures.
The getaway is a new well, new pipes, with a new hand pump. They still make ‘em. I do have to filter for drinking water, and I have a Big Berkey™ Water Filter, counter top model for that. You could put ditch water through it and its drinkable.