Hi bwomp,
I’ve never slept on Celsion (now called Talalay GL) but like other types of mattress components it uses a phase change material added to the latex which absorbs some heat and changes “phase” to more of a liquid and then returns the heat when it cools down and becomes more solid again. In other words it “regulates” in both directions. It can make a difference in temperature regulation but is only part of the “sleeping cool” dilemma. You could certainly ask them if they could add it as a special order and what the extra cost may be if they can. Talalay is already very breathable though so it may be enough in combination with other parts of your sleeping system.
The last part of post #4 here from yesterday may be of interest to you because sleeping temperature has many factors and the most important part of a cool and temperature regulating sleeping environment is ventilation and the control of humidity next to the skin. The upper layers of a mattress are only part of this. The ticking/quilting (synthetic fibers absorb less moisture and are less temperature regulating and wool in the quilting is good for this because it can absorb moisture and promotes ventilation) along with your choice of a mattress protector, sheets, and bedding will also play a big role. If you go outside on a hot day … the relative humidity will play as big a role in how hot you feel (and how much you perspire) as the temperature itself so keeping low humidity levels next to the skin is important regardless of whether you are a degree or two cooler.
Phoenix