Wouldn't just a small capacitor across the voltmeter coil make it more tolerant to the PWM nature of the input and allow it to move more?
Yes if we ever get to the point of actually trying something and seeing the results and finding the pointer vibrated too much, it would help.
But until some one tries something we will never know.
What do you mean?
You could not find a meter with 3V or 5V scale?
Did you look on the scale and see if it had a mA or uA rating.
Most meters that are scaled say 5V, are actually a basic meter movement that needs an external series resistor to read voltage correctly on the scale.
Did you check out meters with mA scales, they can be made to read any voltage within reason you choose with a scaling resistor?