Good idea,do you have any way of limiting how lean or rich you can go with the screw?
I deal with small 2-stroke engines at work and have always wondered why they did not manufacture dirt bikes with a carb with external adjustment screws for the high and low speed circuits(we have the pilot screw,low speed ),you could even put in a screw for the mid range,most of the motors I deal with now have limiting blocks so you cannot lean or richen them out to far to damage the motor.The terrain we have here runs from sea level(warm) up to snow level (cold),you could simply give the circuit you wish to adjust a tweek for peak performance.
Might be ideal to fab up one into the drain plug with a external high speed screw(main).