An alternative approach is to use a LM3914 to drive the LEDs, with an external 10-resistor ladder powered from the reference voltage. Then the rotary switch simply selects a voltage from the ladder which will light the required number of LEDs.

This is just an outline; for example, the topmost resistor of the ladder would be selected to set the step voltages within the tolerance (which in my experience is pretty tight) of the LM3914 comparators.