Control variable resistance with CDS cell and PWM-driven incandescent lamp?

The only problem I can foresee is matching the value of the pot to the CDS cell. You might have to use more than one and wire them in series or parallel.
Also make sure it is a variable resistance rather that a pot. If it is a pot you might have trouble getting end to end tapping control. That means you would have to have one end as a fixed resistor and that would prevent the tap point ever looking like the top end.