am I going in the wrong direction?

I hate those rubber band TBs, that have a mind of their own.
It's cable throttle or nothing for this cowboy.

If I was in your most enviable position, I would convert it to a stand alone EFI with a throttle cable TB. If that is not possible then, no thanks.If I can't be in charge of something around here I'll go mad. Men were born to be leaders. Take control of your design rite. We pee standing UP, so we can be ready to fight.
The DA that authorized electronic throttle control into service deserves a good swift kick in the peanuts.