You know Bert, you have the right Idea with the solenoid valve being grafted onto an existing carbs. That would be for the average flyer that wants to get their engine converted over to running on gas. and for the individual setup with machine equipment to make their own throttle body, most likely those individuals like Cat1 have the aptitude and skill to do so.

If you could come up with means of attaching the solenoid to the main needle threaded portion, that would work. you could have the threaded portion with a taper that replaces the main needle, and the entire solenoid housing can be turned / rotated to trim the fuel mixture while setting up the mixture curve. could be either a straight in threaded housing, or possibly a 90 degree so it fits inside the cowling.

And those Perry carbs could work out well due to the composite carb body, which makes a good thermal insulator. there's plenty of Perry carbs models available to fit most glow engines. Of course you wouldn't have to provide the carb in the kit, just the information, and the basic essentials, like you're doing now, and let the enduser acquire the carb as needed.