A. Trying to design down to two knobs makes each knob multi-modal. This removes a lot of muscle memory benefits requiring a glance at a screen, a small screen that is now partially covered by your hand while operating the knob. Haptic feedback might be able to help you know what mode you're in without looking but now you have a lot more to memorize to use it while keeping your eyes on the road which may begin to defeat the simplicity benefits.
B. Haptic feedback... will this work with gloves on? (will you feel it, will it sense your touch)
A lot of manual systems now have 3 knobs, not much more than the 2 presented here, which will always do the same thing each time you reach for them. My concern would be how long it would take the user to be familar with the interface without looking. One quick thought, I would be inclined to think that feedback through a large screen not covered by your fingers might have advantages.
It's a great study on UI consistancy however, esp around how to program the detents, etc.