This was basically what I was thinking about when I posed this question:
It seems that it would be easier to draft new parts than try to modify an existing part to get what you want.
I'm reasonably certain this can be done in two 3d printed parts: a body+rail single unit, and a new grip.
It's the grip that I currently have no design for. The trigger would have to change as pictured into a direct actuated sear.
"Accuracy by aiming."
Definitely not on the A-Team.