I'm looking for a wooden peel 14" in width, without tapered or angled edges, which is also thin or decreases in thickness to the tip -- any suggestions?
If I am understanding your needs correctly, you DO NOT what the traditional "beveled" leading edge, but want a thin "wedge" shaped peel that increases in thickness from the leading edge "0" to whatever the final thickness of the peel handle is. Sound like a big wedge with a handle and most likely it will need to be custom made. I'm sure there are woodworkers who could make one for you.
The thinnest wooden (well, composite wood) 14" wide peel that I know of is the Epicurean Peel. I have one and it works pretty good for launching traditional pizzas, but not sticky gluten-free ones. It does have the traditional beveled leading edge, but the bevel is longer than most.
Hope this helps and take care!