Nope, won't work... In theory, it should, but in reality, it is two throttlevalves in series, where the servo controlled valve will ONLY have a noticable effect when its passage approaches that of the main needle, leading to a very abrupt control and a very narrow usable range.

The trick with the modulating solenoid, is that it is an on/off switch, basically, and the actual metering is still done with the manual needle valve itself. The solenoid opening and closing imposes a "dutycycle" on the flow through that main needle, allowing for a very linear and precise control of the actually metered mount of fuel.

Say your fuel tube allows for a full flow of 100 ml per minute, and you trim the main needle back to the 10 ml/min the engine actually needs at full throttle.
A servo-operated throttlevalve in the fuel line will only have a noticable effect on the flow if its passage closes all the way from full flow down to 10 ml/min or less. Meaning a lot of the actual throw is not effective, and the actual control all needs to be done in that last 10% of servo travel. The slightest amount of friction or play in the mechanical linkage will destry any remaining accuracy and repeatability.

The solenoid allows you to set the main needle at 11 ml/min (a touch rich, providing some headroom for the atmospheric compensation) and a 91% dutycycle will then interrupt that flow of 11 ml/min to the exact value needed. Meaning you still have approx 90% of the full linear range availlable to control down when the throttle is reduced.