I'm not sure that it is that big of deal here in the rust belt for the fact that the liquid brine which the governments are all addicted to acts as a moisture magnet anyway. It will absorb moisture at ANY temperature, which makes it great for dust control on gravel roads, but lousy stuff to have attached to your car at any time. Also considering that it is corrosive, it will do far more damage than humidity from a damp garage. Besides, cold air holds less moisture than warm air.
Also, in a radiant heated environment, the rust issue would be minimized because you are heating the objects inside the garage rather than heating the air. I've been in many shops heated to 50 degrees where there was a 30 degree difference between the floor and the ceiling. With forced air you've got to run it warmer to compensate for the less efficient heating at the floor level.
Any time I've had rust issues with stuff in a garage (unheated), it was a result of condensation due to a warm day, cold concrete, cold tool box, cold tools, etc.; and always in the spring. With radiant heating, this problem is minimized because the coldest objects in the space which create the condensation are warmer.