Searching for an analog circuit solution, where an output voltage is incremented or decremented based on an input
You need a closed loop control circuit such as one where the opamp's feedback comes from the output. In effect the mosfet (or external transistor) becomes regarded as part of the opamp. The opamp will then deliver whatever control voltage is needed to the transistor in order to make the output equal the demand.

On your circuit the opamp has local feedback but if this were removed and replaced with overall feedback you will get what I believe you are requiring. It's a little trickier though because circuits like this can be unstable but there are many examples of a MOSFET or BJT being used this way. Typical of this is the ubiquitous 7805 voltage regulator. It's demand is fixed internally and it uses overall feedback and internal high gain amplification to regulate the output voltage to 5 volts.

Here's a great example of an op-amp driving a bunch of power transistors but taking its feedback directly after the transistors i.e. the op-amp is "measuring" the output and correcting the anomalies output by driving the transistors harder or lighter as required: -



Here's a simpler circuit where the op-amp is "measuring" the output current and ensuring that it remains constant over a large load range: -



Note that the feedback point comes not from the op-amp's output but from the resistor above the transistor.