The trouble I
get is from solder joints that can't stand up to a freeze, where
cemented plastic pipe can.

Where do you get that idea! I live in the land of the cold, and had a number
of soldered copper pipes freeze when I didn't drain them properly. In my
experiences, if the solder joint is done properly, it will not fail but the
pipe will split. Better is to prevent the pipes from freezing as the frozen
pipe will be damaged in one way or another. When ice is formed it expands
and can split a pipe, crack an elbow, or damage the hardest rock or
concrete. You need to either use insulation or heat to correct the problem
or change the location.