>(or even better, the voltage level from the disc itself but one thing at a time).
The voltage level from the disc is rather boring as it's just on or off.
I have a vague recollection that some discs had the PWM modulation done digitally and some were analogue. For the latter sampling from the laser pickup could be less accurate than sampling after the PWM demodulation.
And you're still gambling that you can decode the video digitally better than your laser disc player.