[HO455]

The drawback of using the old resistor wire circuit for alternator sensing is if you have a voltage drop (Say 2 volts) in the circuit between the battery and the end of old resistor circuit at the alternator. The alternator would begin charging to bring the voltage it was sensing up to 14.5 volts. At that point your voltage to the battery would be 16.5 volts. Voltage sensing to control the alternator output should come from the battery. Batteries not tolerant of over or under charging.
There are too many points (i.e. connections and switches) for a voltage drop(s) to develop between the battery and the alternator sensing using the old resistor wire circuit for my comfort level. Just my opinion.
Have you read the Mad Electrical information on alternator operation? It may help answer your questions.
Here is the link if not.

http://www.madelectrical.com/electrical-tech.shtml