Ingredients vs. Temperature Control in Chocolate Fudge
I think you may well be over thinking this just a little.

Water boils at 100c at sea level, sugar raises this temperature to around 110c depending on sugar content.


  Specifically, adding 1 gram molecular weight of nonionizing solute (like sugar) to 1 liter of water increases the boiling point by 0.52 degree Celsius (C). 1 gram molecular weight nonionizing solute per liter =0.52 degree C increase in boiling point.


So when you boil your sugar syrup to soft ball 116c you've essentially, boiled all the water away and your left with sugar. Heating it to this temperature changes the shape and direction of the crystals. Adding fat to this generally allows it to set (plus flavour). Just as butter would.

The reason you don't add chocolate as it's warming is water plus chocolate ends badly. You also don't add it at 116c as you will burn your chocolate. Again not a good thing. 


  Make sure the temperature of the chocolate rises to between 104° F. and 113° F. when melting. Do not heat above 115° F. (milk and white chocolate) and 120° F. for dark chocolate, otherwise it will burn.


The reason you add water to sugar is to allow more control over the heating. If you have no water you'll find the bottom part will burn while the top part is still solid crystals. Which considering you only need 116c, is again... Bad.

Try boiling 1000ml water with 100g sugar and see how quickly it takes for the mixture to reach 110c (5min?) and then see how long it'll stay at that temperature before hitting 116 (30-40mins I guess). Then leave it and watch how within moments of hitting 116c it's suddenly hit 176c and then your pan turn black and your kitchen full of thick yellow smoke :-).