I would say that Instead of water circulating to stop it freezing the product lines.
it would use glycol/Antifreeze this will be inside the cold plate. which the product tubing will pass through.
Hey, this is the machine to have, its much simpler and will produce better tasting soda than Post mix, as you don't have syrups moldering around in the product tubes.
The product will stay nice and fresh + you can also dispense beer through it.
You'l need to see if you can get Premix tanks from Coke Or Pepsi, if you cant you can make it your self, just get a Soda keg for each carbonated product you won't then place 4L of Syrup inside the Keg Fill it up with plain water, place in the fridge overnight with co2 Gas connected. Wham bam your'v got Soda. then Connect it up to the dispenser.
Not that you need to Chile the product while carbonating it, you may find it easer to place all the kegs in a Fridge and then run the Tubes to Your Dispenser.
You could also dispense a non carbonated product like Real Orange Juice, Apple Juice, or Wine. You'l need to Get these in bag'n Box (ready to drink) Simply connect the bag'n box to a Syrup Pump then run a line from the pump to your Premix dispenser