"Insulate the walls of the basement which stick out of the ground about 4' and it'd probably stay 70° down there with no direct heating of it."
For reasons that never were explained, my mom and her brother decided my grandparents' perfectly operating boiler 'had' to be replaced. I warned that the basement temps would drop sharply, causing cold floors, cold basement, no place to dry clothes in the winter, pipes more apt to freeze, etc.
Since this info came from me, it was ignored. The boiler was replaced and when the consequences I warned of came, I was told it was a coincidence.
I'd leave the system as is and enjoy its benefits.