Is the following system viable do you think?

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The idea is for pulley B to be powering something like a circular saw than can be raised or lowered by moving the green bit, either through a lever or stepper-controlled screw, etc.

The reason for this kind of setup is because that same motor could be used to power another tool located nearby - not at the same time, of course. The tool that is not in use could be retracted beneath the table and disconnected from the motor perhaps.