Newt,
I have re-mouthed wood planes in the past with an inlay of hardwood. I make it a broad wedge (trapezium) shape in plan, with the narrower part pointing forwards to the toe of the plane - about 3mm thick)
Newt - the traditional way was just to inlay a bit about 6mm thick and 30mm or so wide in front of the cutter to close up the mouth. Once the glue has set the complete sole can be shot true with a longer plane - Rob