You could achieve both your core requirements from the final two paragraphs by having, effectively, a slider control underneath the rotary dial. The slider is t

You could achieve both your core requirements from the final two paragraphs by having, effectively, a slider control underneath the rotary dial. The slider is the actual control — behaving as you describe in para 2 — and the rotary dial is merely for pleasing visual feedback. The GUI would have to emphasise the roles of those two separate parts somehow.