Will:
If you think something more than 'converting' a cooler to a heater is necessary here, we are in complete agreement.
I believe we are in agreement and I think any heating needs to be upstream in the wing to help prevent icing in the pipes as was experienced in testing.
Chris, yes it is the fuel but I think it more practical (cheaper) to modify the planes so that they can better tolerate water than to change the specs. Trying to keep water, and other undesirable materials, out of the fuel would be much more expensive and more frustrating than a strategically located heater in the airplane.