So now we have the regulator as thermostat. OK fine if you say so. ---- go ahead and use your cnstant, regulator. Electricity is charge does create heat, heat is what damages the system including the battery and alternator. Using a regulator controls this electricla flow.
http://www.autoshop101.com/trainmodules/alternator/alt131.html
The regulator will attempt to maintain a pre-determined charging system voltage level.

When charging system voltage falls below this point, the regulator will increase the field current, thus strengthening the magnetic field, which results in an increase of alternator output.

When charging system voltage raises above this point, the regulator will decrease field current , thus weakening the magnetic field, and results in a decrease of alternator output.
Also - http://www.familycar.com/Classroom/charging.htm
The voltage regulator can be mounted inside or outside of the alternator housing. If the regulator is mounted outside (common on some Ford products) there will be a wiring harness connecting it to the alternator.

The voltage regulator controls the field current applied to the spinning rotor inside the alternator. When there is no current applied to the field, there is no voltage produced from the alternator. When voltage drops below 13.5 volts, the regulator will apply current to the field and the alternator will start charging. When the voltage exceeds 14.5 volts, the regulator will stop supplying voltage to the field and the alternator will stop charging. This is how voltage output from the alternator is regulated. Amperage or current is regulated by the state of charge of the battery. When the battery is weak, the electromotive force (voltage) is not strong enough to hold back the current from the alternator trying to recharge the battery. As the battery reaches a state of full charge, the electromotive force becomes strong enough to oppose the current flow from the alternator, the amperage output from the alternator will drop to close to zero, while the voltage will remain at 13.5 to 14.5. When more electrical power is used, the electromotive force will reduce and alternator amperage will increase. It is extremely important that when alternator efficiency is checked, both voltage and amperage outputs are checked. Each alternator has a rated amperage output depending on the electrical requirements of the vehicle. About the same as hooking up and forgetting a constant, non voltage controlled battery charger of past years. Wouldn't think of doing that - would you?