Just to add alittle to the Headlight dimming and the cap issue. Take the
cars charging system. Simulations lack Time Lag for the Regulator to pick
up
on a Voltage fluctuation.

Not if you make the current draw frequency low enough. You could even
attempt to simulate the PWM action by putting a high frequency in the low
freq envelope. But it's unnecessary for our purposes.

Not to mention that the Cars electrical system is
run buy the alt when running.

That's easily simulated. Just raise the voltage and modify the output Z.
Or if you want to get really fancy, put a second source in parallel.

WHen demads are high enough the Alt cannot
keep up and we have Voltage sag, which inturn drops the enitire voltage of
the charging system.

Seeing that almost all electrical components are in parallel with the Alt
and battery. That fluctuation will be felt throughout the electrical
system.
So those that say if a 50A draw causes a 1V flucuation at the amp that sag
will be produced throughout the entire system.

Correct. The fluctuation is the result of the output impedance of the
source.

Not to mention that most auto manufactures do not use the best techniques
for wiring Headlights. Their are reasons why wpoplw rewire Headlights with
Bigger Ga. Wire, Relay's and use the Head light switch wiring for Relay
activation.

Right. Many manufacturers run the headlight power all the way to the dash,
through the switches, and back again. People often modify the circuit so
this wire drives a relay. This is done to improve the total output of the
headlights. But it actually does not improve the flickering!