How can I modify corn bread recipes to accomodate a wet filling?
I agree that cornbread will not have the structure you need since it's close to a sponge cake.  Instead of modifying a cornbread recipe, I would recommend modifying a pie crust recipe. 

A standard pie crust is approximately 3 parts flour : 2 parts fat : 1 part water. To achieve the cornbread flavors, replace some of the flour with the cornmeal, as it can serve the same purpose as flour in this case. You can also replace some or all of the water with milk or buttermilk. If you do not like the grainy texture of the cornmeal, soak the cornmeal in the liquid you choose for several hours to overnight.