MOTM

I would favor just the opposite.
A larger coarse knob for broad sweeps and a smaller fine knob for 
getting exactly the tuning you want when a fixed setting is called 
for.  For live performance you could still get very close with the 
large coarse knob and then tweak it with the smaller knob.
OR . . .
How about 2 large knobs one for coarse and one for fine?