Your engine's cooling system Needs a thermostat to properly function. Ive professionally raced for Years and have seen this tested over and over and over. With out a proper thermostat in place, its not so much that your engine will not hit operating temperature. The issue is that the coolant is now flowing too fast through the system to properly remove heat from your heads. The coolant will not be up to temperature, however your heads will be developing hotspots. The coolant needs to be slowed down to work properly. You need that thermostat. More so in a Diesel or multi.
As for electric fans, flex-a-lite fans (monster and black magic) can be wired to function on 24 volt. I have personally confirmed this with the factory. Get 2 of the 15" fans, hook them up and be ready to go.
Yes, the water pump pulls a bit of power. But thats nothing in caparison to what the fan does. If you have ever had your clutch fan go bad on your daily driver, then you know just how much power a fan can suck from your engine. Replacing the stock fan on our rigs with electric, I Guarantee you will free a substantial amount of power. And with our rigs, every hp counts.